Golf shaft system and golf shaft

Abstract

A golf club shaft system and golf club shaft having a unique bending and torsional stiffness profile while providing significant adjustability to fine tune the shaft to a particular golf swing.

Description

TECHNICAL FIELD

[0001] The present invention relates to sports equipment, and more particularly to a golf club shaft. BACKGROUND

[0002] During the swing of a golf club, the shaft experiences loads and tends to deflect and twist. Few realize that this deflection and twist also occurs during the putting stroke, especially when the putter head mass is increased, but to a much lesser extent. As used herein, "stability" of the shaft refers to the degree to which the toe and heel of the face move in alignment with each other during the stroke. The relative fluctuations in the velocity and acceleration of the toe and heel of the face before, during, and after the stroke can be significantly improved. Controlling the face angle and face twist results in a narrower range of departure angles for the ball off the face and significantly improves the likelihood that the ball will leave the face at an angle closer to the target line, which improves the likelihood of achieving a hole-in-one on the putting stroke.

[0003] While the #1 wood, fairway metal, and hybrid shafts have evolved from steel tubes to a wide variety of often complex composite shafts over the past 30+ years, the putter shaft has not evolved as rapidly. Serious golfers do not believe that their #1 wood can perform at its best with an inexpensive steel shaft. Why would serious golfers believe that their putter is best suited for a cheap steel shaft when better options are available? After all, the putter is used almost twice as much as any other club in the bag. Most traditional putter shafts are simply steel tubes (wrapped and welded construction) that contain little, if any, engineering tailored to the unique circumstances of the putter. These putter shafts are narrow at the tip and gradually increase in diameter at the butt end for grip purposes, thus exhibiting inherent weakness in the lower portion of the shaft. Ultimately, the reason steel shafts continue to dominate is cost: putter manufacturers primarily use steel shafts because they are very inexpensive.

[0004] The present invention provides a significant advance tailored to the putter, but is equally applicable to all golf shafts. In fact, embodiments of the present invention enable a golfer or professional fitness person to easily tailor the characteristics of a putter or any other club to the individual's golf swing. SUMMARY

[0005] A golf club shaft having a butt portion joined to a tip portion by a coupler and possessing unique relationships including a stiffness relationship that provides beneficial performance characteristics, including increased stability and adjustability. BRIEF DESCRIPTION OF DRAWINGS

[0006] Without limiting the scope of the invention as claimed below, reference is now made to the drawings in which: 1. A golf club shaft having a butt portion joined to a tip portion by a coupler and possessing unique relationships including a stiffness relationship that provides beneficial performance characteristics, including increased stability and adjustability. 2. The golf club shaft of claim 1, wherein the stiffness relationship is a function of the stiffness of the butt portion, the stiffness of the tip portion, and the stiffness of the coupler. 3. The golf club shaft of claim 1, wherein the stiffness relationship is a function of the stiffness of the butt portion, the stiffness of the tip portion, and the stiffness of the coupler. 4. The golf club shaft of claim 1, wherein the stiffness relationship is a function of the stiffness of the butt portion, the stiffness of the tip portion, and the stiffness of the coupler. 5. The golf club shaft of claim 1, wherein the stiffness relationship is a function of the stiffness of the butt portion, the stiffness of the tip portion, and the stiffness of the coupler. 6. The golf club shaft of claim 1, wherein the stiffness relationship is a function of the stiffness of the butt portion, the stiffness of the tip portion, and the stiffness of the coupler. 7. The golf club shaft of claim 1, wherein the stiffness relationship is a function of the stiffness of the butt portion, the stiffness of the tip portion, and the stiffness of the coupler. 8. The golf club shaft of claim 1, wherein the stiffness relationship is a function of the stiffness of the butt portion, the stiffness of the tip portion, and the stiffness of the coupler. 9. The golf club shaft of claim 1, wherein the stiffness relationship is a function of the stiffness of the butt portion, the stiffness of the tip portion, and the stiffness of the coupler. 10. The golf club shaft of claim 1, wherein the stiffness relationship is a function of the stiffness of the butt portion, the stiffness of the tip portion, and the stiffness of the coupler. 11. The golf club shaft of claim 1, wherein the stiffness relationship is a function of the stiffness of the butt portion, the stiffness of the tip portion, and the stiffness of the coupler. 12. The golf club shaft of claim 1, wherein the stiffness relationship is a function of the stiffness of the butt portion, the stiffness of the tip portion, and the stiffness of the coupler. 13. The golf club shaft of claim 1, wherein the stiffness relationship is a function of the stiffness of the butt portion, the stiffness of the tip portion, and the stiffness of the coupler. 14. The golf club shaft of claim 1, wherein the stiffness relationship is a function of the stiffness of the butt portion, the stiffness of the tip portion, and the stiffness of the coupler. 15. The golf club shaft of claim 1, wherein the stiffness relationship is a function of the stiffness of the butt portion, the stiffness of the tip portion, and the stiffness of the coupler. 16. The golf club shaft of claim 1, wherein the stiffness relationship is a function of the stiffness of the butt portion, the stiffness of the tip portion, and the stiffness of the coupler. 17. The golf club shaft of claim 1, wherein the stiffness relationship is a function of the stiffness of the butt portion, the stiffness of the tip portion, and the stiffness of the coupler. 18. The golf club shaft of claim 1, wherein the stiffness relationship is a function of the stiffness of the butt portion, the stiffness of the tip portion, and the stiffness of the coupler. 19. The golf club shaft of claim 1, wherein the stiffness relationship is a function of the stiffness of the butt portion, the stiffness of the tip portion, and the stiffness of the coupler. 20. The golf club shaft of claim 1, wherein the stiffness relationship is a function of the stiffness of the butt portion, the stiffness of the tip portion, and the stiffness of the coupler. 21. The golf club shaft of claim 1, wherein the stiffness relationship is a function of the stiffness of the butt portion, the stiffness of the tip portion, and the stiffness of the coupler. 22. The golf club shaft of claim 1, wherein the stiffness relationship is a function of the stiffness of the butt portion, the stiffness of the tip portion, and the stiffness of the coupler. 23. The golf club shaft of claim 1, wherein the stiffness relationship is a function of the stiffness of the butt portion, the stiffness of the tip portion, and the stiffness of the coupler. 24. The golf club shaft of claim 1, wherein the stiffness relationship is a function of the stiffness of the butt portion, the stiffness of the tip portion, and the stiffness of the coupler. 25. The golf club shaft of claim 1, wherein the stiffness relationship is a function of the stiffness of the butt portion, the stiffness of the tip portion, and the stiffness of the coupler. 26. The golf club shaft of claim 1, wherein the stiffness relationship is a function of the stiffness of the butt portion, the stiffness of the tip portion, and the stiffness of the coupler. 27. The golf club shaft of claim 1, wherein the stiffness relationship is a function of the stiffness of the butt portion, the stiffness of the tip portion, and the stiffness of the coupler. 28. The golf club shaft of claim 1, wherein the stiffness relationship is a function of the stiffness of the butt portion, the stiffness of the tip portion, and the stiffness of the coupler. 29. The golf club shaft of claim 1, wherein the stiffness relationship is a function of the stiffness of the butt portion, the stiffness of the tip portion, and the stiffness of the coupler. 30. The golf club shaft of claim 1, wherein the stiffness relationship is a function of the stiffness of the butt portion, the stiffness of the tip portion, and the stiffness of the coupler. 31. The golf club shaft of claim 1, wherein the stiffness relationship is a function of the stiffness of the butt portion, the stiffness of the tip portion, and the stiffness of the coupler. 32. The golf club shaft of claim 1, wherein the stiffness relationship is a function of the stiffness of the butt portion, the stiffness of the tip portion, and the stiffness of the coupler. 33. The golf club shaft of claim 1, wherein the stiffness relationship is a function of the stiffness of the butt portion, the stiffness of the tip portion, and the stiffness of the coupler. 34. The golf club shaft of claim 1, wherein the stiffness relationship is a function of the stiffness of the butt portion, the stiffness of the tip portion, and the stiffness of the coupler. 35. The golf club shaft of claim 1, wherein the stiffness relationship is a function of the stiffness of the butt portion, the stiffness of the tip portion, and the stiffness of the coupler. 36. The golf

[0007] Figure 1 An elevational view of a golf club is not shown to scale;

[0008] Figure 2 shows a perspective view of one embodiment of a golf shaft not to scale;

[0009] Figure 3 shows an exploded perspective view of one embodiment of a golf shaft not to scale;

[0010] Figure 4 Figure 4 shows a perspective cross-sectional view of one embodiment of a golf shaft not to scale;

[0011] Figure 5(A) shows a side view of one embodiment of a tip section not to scale;

[0012] Figure 5(B) shows an end view of one embodiment of a tip section not to scale;

[0013] Figure 6(A) shows a side view of one embodiment of a butt section not to scale;

[0014] Figure 6(B) shows an end view of one embodiment of a butt section not to scale;

[0015] Figure 7(A) shows a side view of one embodiment of a butt section insert not to scale;

[0016] Figure 7(B) shows an end view of one embodiment of a butt section insert not to scale;

[0017] Figure 8(A) shows a side view of one embodiment of a coupler not to scale;

[0018] Figure 8(B) shows a side view of one embodiment of a coupler not to scale;

[0019] Figure 9 Figure 9 shows a graph of the shaft stiffness profile of one embodiment of a golf shaft not to scale;

[0020] Figure 10 Figure 10 shows a graph of the shaft stiffness profile of one embodiment of a golf shaft not to scale;

[0021] Figure 11 Figure 11 shows a graph of the shaft stiffness profile of one embodiment of a golf shaft not to scale;

[0022] Figure 12 Figure 12 shows a graph of the shaft stiffness profile of a conventional step golf shaft not to scale;

[0023] Figure 13(A) shows a graph of the heel and toe velocities of the putter head at impact, not to scale;

[0024] Figure 13(B) shows a graph of the heel acceleration and toe acceleration of the putter head at putter impact, not to scale;

[0025] Figure 14(A) shows a table of heel and toe velocities of the putter head at impact, not to scale;

[0026] Figure 14(B) shows a graph of the heel acceleration and toe acceleration of the putter head at putter impact, not to scale;

[0027] Figure 15 An exploded perspective view of one embodiment of a golf club shaft system is shown out of scale.

[0028] Figure 16 A perspective view of one embodiment of a golf club shaft is shown out of scale;

[0029] Figure 17 A side view of one embodiment of the tip portion is shown out of scale;

[0030] Figure 18 The diagrams illustrating the characteristics of different tip portions in one embodiment are not shown to scale;

[0031] Figure 19(A) is a graph showing the shaft stiffness distribution of one embodiment of the tip portion, not to scale, where the vertical axis is in N*m. 2 The horizontal axis is in inches;

[0032] Figure 19(B) is a graph showing the shaft stiffness distribution of one embodiment of the tip portion, not to scale, where the vertical axis is in N*m. 2 The horizontal axis is in inches;

[0033] Figure 19(C) shows a graph of shaft stiffness distribution at the tip of one embodiment, not to scale, where the vertical axis is in N*m. 2 The horizontal axis is in inches;

[0034] Figure 19(D) is a graph of the shaft stiffness distribution of an embodiment at the tip, not shown to scale, where the vertical axis is in N*m. 2 The horizontal axis is in inches;

[0035] Figure 20 A table showing the shaft stiffness distribution of an embodiment with the tip portion is not shown to scale;

[0036] Figure 21 A partial cross-sectional view of an embodiment of a connector is shown out of scale;

[0037] Figure 22 A partial cross-sectional view of an embodiment of a connector is shown out of scale;

[0038] Figure 23(A) is a graph showing the shaft stiffness distribution of one embodiment of the tip portion, not to scale, where the vertical axis is in N*m. 2 The horizontal axis is in inches;

[0039] Figure 23(B) is a graph showing the shaft stiffness distribution of one embodiment of the tip portion, not to scale, where the vertical axis is in N*m. 2 The horizontal axis is in inches;

[0040] Figure 23(C) is a graph showing the shaft stiffness distribution of one embodiment of the tip portion, not to scale, where the vertical axis is in N*m. 2 The horizontal axis is in inches;

[0041] Figure 23(D) is a graph showing the shaft stiffness distribution of one embodiment of the tip portion, not to scale, where the vertical axis is in N*m. 2 The horizontal axis is in inches;

[0042] Figure 24 A graph showing the shaft stiffness distribution of one embodiment of the tip portion is not shown to scale, with the vertical axis in N*m units. 2 The horizontal axis is in inches; and

[0043] Figure 25 A graph showing the shaft stiffness distribution of one embodiment of the tip portion is not shown to scale, with the vertical axis in N*m units. 2 The horizontal axis is in inches.

[0044] These accompanying drawings are provided to aid in understanding exemplary embodiments of the invention as described in more detail below, and should not be construed as unduly limiting the scope of the invention. Specifically, the relative spacing, positioning, size, and dimensions of the various elements shown in the drawings are not drawn to scale and may be exaggerated, reduced, or otherwise modified for clarity. Those skilled in the art will also understand that a range of alternative configurations have been omitted solely for clarity and to reduce the number of drawings. Detailed Implementation

[0045] The detailed description given below in conjunction with the accompanying drawings is intended only as an illustration of the presently preferred embodiments of the invention and is not intended to represent the only forms in which the invention can be practiced or utilized. The description, in conjunction with the illustrated embodiments, gives designs, functions, devices, and methods for implementing the invention. However, it should be understood that the same or equivalent functions and features can be implemented through different embodiments, which are also intended to be included within the spirit and scope of the invention.

[0046] like Figures 1-8(B) As shown, an embodiment of the shaft 100 of the present invention includes a distal shaft 110, a proximal shaft 120, a shaft outer diameter, and a shaft mass, wherein each point along the shaft length 130 has a shaft bending stiffness (generally abbreviated as EI) and a shaft torsional stiffness (generally abbreviated as GJ). The shaft 100 may include a root portion 1000 joined to a tip portion 2000 by a connector 3000, wherein the connector 3000 may permanently or releasably attach the root portion 1000 to the tip portion 2000. It must be understood that the shaft bending stiffness and shaft torsional stiffness can be taken at points along the shaft length 100, taking into account the region of the shaft 100 composed of multiple elements within a cross-section perpendicular to the shaft axis, and the bending stiffness and torsional stiffness of a particular element, disclosed later, are associated only with that particular element and not with the combination of elements that may constitute the shaft 100.

[0047] Referring specifically to Figures 6(A) and 6(B), the root portion 1000 has a distal end 1010, a proximal end 1020, a length 1030, a sidewall 1040 with a sidewall thickness 1050, an inner diameter 1060, and an outer diameter 1070. Similarly, referring specifically to Figures 5(A) and 5(B), the tip portion 2000 has a distal end 2010, a proximal end 2020, a length 2030, a sidewall 2040 with a sidewall thickness 2050, an inner diameter 2060, and an outer diameter 2070. In some embodiments, the tip length 2030 is not longer than 65% of the root length 1030, while in some additional embodiments, at least a portion of the tip portion 200 has a tip outer diameter 2070 that is at least 25% smaller than the outer diameter 1070 of a portion of the root portion 1000. Further, referring specifically to Figures 8(A) and 8(B), the connector 3000 has a connector distal end 3010, a connector proximal end 3020, a connector length 3030, a connector sidewall 3040 having a connector sidewall thickness 3050, a connector inner diameter 3060, and a connector outer diameter 3070. In one embodiment, at least a portion of the root portion 1000 has a root portion sidewall thickness 1050 that is greater than the tip portion sidewall thickness 2050 of a portion of the tip portion 2000; in another embodiment, the root portion sidewall thickness 1050 is at least 15% thicker than the tip portion sidewall thickness 2050; and in yet another embodiment, the root portion sidewall thickness 1050 is at least 25% thicker than the tip portion sidewall thickness 2050.

[0048] The root portion sidewall thickness 1050 is no greater than 0.125" in one embodiment, no greater than 0.100" in another embodiment, and no greater than 0.085" in yet another embodiment. A further series of embodiments introduces a minimum root portion sidewall thickness 1050 of at least 0.020" in one embodiment, at least 0.025" in another embodiment, and at least 0.030" in yet another embodiment. In a particularly effective embodiment, the maximum tip portion sidewall thickness 2050 is greater than the maximum root portion sidewall thickness 1050, at least 0.005" greater in one embodiment, at least 0.015" greater in another embodiment, and at least 0.020" greater in yet another embodiment. The maximum tip portion sidewall thickness 2050 is preferably no greater than 0.125" in one embodiment, no greater than 0.100" in another embodiment, and no greater than 0.080" in yet another embodiment. The root portion sidewall thickness 1050 and / or the tip portion sidewall thickness 2050 can vary along the length. In one embodiment, the root portion sidewall thickness 1050 increases to a maximum thickness located within a distance equal to twice the connector length 3030 from the proximal end 1020 of the root portion, while in another embodiment, it is located within a distance of 6" from the proximal end 1020 of the root portion. In another embodiment, the root portion sidewall thickness 1050 changes from a minimum thickness to a maximum thickness that is at least 5% thicker than the minimum thickness, in another embodiment, it is at least 10% thicker, and in yet another embodiment, it is at least 15% thicker. Similarly, in a similar series of embodiments, the tip portion sidewall thickness 2050 changes from a minimum thickness to a maximum thickness that is at least 5% thicker than the minimum thickness, in another embodiment, it is at least 10% thicker, and in yet another embodiment, it is at least 15% thicker.

[0049] In another embodiment, the average connector sidewall thickness 3050 over the entire connector length 3030 is greater than the average root portion sidewall thickness 1050. In yet another embodiment, the average connector sidewall thickness 3050 is greater than the average tip portion sidewall thickness 2050. In yet another embodiment, the average connector sidewall thickness 3050 is at least 15% thicker than the average root portion sidewall thickness 1050. In yet another embodiment, the average connector sidewall thickness 3050 is at least 15% thicker than the average tip portion sidewall thickness 2050.

[0050] In some embodiments, the root portion 1000 is formed of a nonmetallic root portion material 1000 having a root material density, a root portion mass of 35%-75% of the shaft mass, a root portion elastic modulus, and a root portion shear modulus, and having a root portion area moment of inertia, a root portion polar moment of inertia, a root portion bending stiffness, and a root portion torsional stiffness at each point along the root portion length 1030. The density of the root portion 1000 may be constant or may vary continuously along the root portion length 1030. Similarly, in some additional embodiments, the tip portion 2000 is formed of a metallic tip portion material having a tip material density, a tip portion elastic modulus, and a tip portion shear modulus that are at least 15% greater than the root material density, and having a tip portion area moment of inertia, a tip portion polar moment of inertia, a tip portion bending stiffness less than the root portion bending stiffness in some embodiments, and a tip portion torsional stiffness less than the root portion torsional stiffness in some embodiments at each point along the tip portion length 2030.

[0051] The material, density, mass, stiffness, inflection point distance, shaft CG distance, and shaft length relationships disclosed herein, both individually and in combination, are crucial to the feel, flexibility, and stability of the shaft 100, producing unexpected benefits when striking a golf ball using the golf club head 5000 attached to the shaft 100. These relationships result in less clubface distortion before, during, and after impact, and improve the consistency of clubface speed with heel and toe accelerations, which will be explained in more detail later with reference to the comparisons of Figures 14(A) and 14(B) with Figures 13(A) and 13(B). Those skilled in the art will understand that during the swing, the golf club shaft bears a load and experiences significant deflection and torsional rotation; however, few realize that such deflection and rotation also occur during putting, especially when the putter head mass increases, albeit at a much smaller rate. As used herein, shaft “stability” refers to the degree to which the toe and heel of the clubface align with each other during impact. These relationships can significantly improve the relative fluctuations in speed and acceleration of the toe and heel of the clubface before, during, and after impact. For example, controlling the clubface angle and clubface twist results in a smaller departure angle of the ball from the clubface and significantly increases the likelihood of the ball leaving the clubface at an angle closer to the target line, which improves the chances of making the putt. Experiments have shown that, depending on the type of putter and the type of shot, a 20%–33% reduction in the putter departure angle does not affect the feel at or after impact. Additionally, especially with low-speed shots associated with putting, these relationships result in a lower launch angle when the ball leaves the clubface. For putters, this means a faster true roll, making the ball's deceleration more predictable and thus providing golfers with better distance control.

[0052] Similarly, as shown in Figure 2, the unique relationship provided by the shaft 100 including a reinforcement zone 2500 between a first point located 5" from the proximal end (120) of the shaft and a second point located 24", 30", or 36" from the proximal end (120) of the shaft further enhances the benefits. See also: Figure 10 In the first section of the reinforced zone 2500, the bending stiffness of the shaft is at least 50% greater than that of the minimum tip section and less than 100 N*m. 2 The torsional stiffness of the shaft is at least 50% greater than the torsional stiffness of the smallest tip portion and less than 100 N*m. 2 Meanwhile, in the second part of the reinforced zone 2500, the bending stiffness of the shaft is at least 50% greater than the bending stiffness of the minimum root section and is greater than 120 N*m. 2 The torsional stiffness of the shaft is at least 50% greater than the torsional stiffness of the minimum root section and is greater than 120 N*m. 2 In another embodiment, "minimum" in the preceding sentence is replaced with "average," and in yet another embodiment, "minimum" in the preceding sentence is replaced with "maximum." Those skilled in the art will understand that these stiffnesses of the tip and root portions can be constant, thus having equal minimum, maximum, and average values; or, these stiffnesses of the mentioned components can be different, thus having different minimum, maximum, and average values. These minimum, maximum, and average value substitutions also apply to all embodiments disclosed herein.

[0053] Therefore, the reinforcing region 2500 has a first portion with significantly higher bending and torsional stiffness than the tip portion 2000, and a second portion with even higher stiffness than the first portion and significantly higher stiffness than the root portion 1000, wherein the stiffness of the root portion 1000 is higher than that of the tip portion 2000. In another related embodiment, the first portion of the reinforcing region 2500 has a bending stiffness at least 75% greater than that of the smallest tip portion and less than 90 N*m. 2 The shaft's bending stiffness, and its torsional stiffness, are at least 75% greater than the torsional stiffness of the smallest tip portion and less than 90 N*m. 2 In yet another relevant embodiment, the second portion of the reinforcing region 2500 has a bending stiffness that is at least 75% greater than that of the minimum root portion and less than 135 N*m. 2 The shaft's bending stiffness, and its torsional stiffness, are at least 75% greater than the minimum root torsional stiffness and less than 135 N*m. 2 .

[0054] In addition, such as Figure 11As shown, a first portion of the shaft 100 extending two-thirds of its length 130 from the proximal end 120 has a first average bending stiffness, and a second portion extending one-third of its length 130 from the distal end 110 has a second average bending stiffness, wherein the first average bending stiffness is at least 50% of the second average bending stiffness, and this specific relationship further enhances the benefits. For comparison, the stiffness of the upper third of a typical steel shaft is more than twice that of the lower two-thirds. In another embodiment, the first average bending stiffness is at least 75% of the second average bending stiffness. In yet another related embodiment, the first average bending stiffness is at least 100% of the second average bending stiffness, and in yet another related embodiment, the first average bending stiffness is 75%-200% of the second average bending stiffness, and in yet another related embodiment, the first average bending stiffness is 100%-150% of the second average bending stiffness.

[0055] Those skilled in the art will understand that the bending stiffness (often also referred to as bending hardness) discussed herein depends on the material hardness or modulus of elasticity (E), and the cross-sectional geometry associated with the area moment of inertia (I), which is why bending stiffness is often referred to as EI. The area moment of inertia (I) of a simple tube is:

[0056]

[0057] Where r o It is the outer radius of the pipe, r i It is the inner radius of the pipe.

[0058] Furthermore, the torsional stiffness (commonly referred to as torsional hardness) discussed in this paper depends on the material's torsional hardness or shear modulus (G), and the cross-sectional geometry associated with the polar moment of inertia (J), which is why torsional stiffness is often referred to as GJ. The polar moment of inertia (J) of a simple tube is:

[0059]

[0060] Where r o It is the outer radius of the pipe, r i It is the inner radius of the pipe.

[0061] Those skilled in the art will understand that these simple equations apply to individual elements; however, when determining the stiffness of the entire shaft's bending and torsional stiffness, there will be points to consider at each level of the elements. For example, as... Figure 4As shown, starting from the tip portion 2000, the calculation is straightforward until the tip portion 2000 enters the connector 3000. At this point, the shaft stiffness calculation must consider the overlap between the connector 3000 and the tip portion 2000. Further into the connector 3000, the shaft stiffness calculation must consider the overlap between the connector 3000, the tip portion 2000, and the root portion 1000. After the connector 3000 and within the separation distance 4080, the shaft stiffness calculation simplifies again until reaching the area of ​​the root insert 4000, where the shaft stiffness calculation must consider both the root portion 1000 and the root insert 4000. This is merely an illustrative example, but it emphasizes the important distinction that the overall shaft bending stiffness and shaft torsional stiffness at various points along the entire shaft length 130 must consider multiple elements, while references to the bending and torsional stiffness of individual components only apply to the individual component being referenced.

[0062] In another embodiment, the previously discussed benefits are further realized in one embodiment, wherein the minimum tip portion bending stiffness is at least 25% less than the minimum root portion bending stiffness, and the minimum tip portion torsional stiffness is at least 25% less than the minimum root portion torsional stiffness. Further still, in another embodiment, the minimum tip portion bending stiffness is 25%-75% less than the maximum root portion bending stiffness, and the minimum tip portion torsional stiffness is 25%-75% less than the maximum root portion torsional stiffness. In another embodiment, the previously discussed benefits are further realized in one embodiment, wherein the minimum tip portion bending stiffness is at least 25% less than the minimum root portion bending stiffness, and the minimum tip portion torsional stiffness is at least 25% less than the minimum root portion torsional stiffness. Further still, in another embodiment, the minimum tip portion bending stiffness is at least 25%-75% less than the minimum root portion bending stiffness, and the minimum tip portion torsional stiffness is at least 25-75% less than the minimum root portion torsional stiffness. The minimum root portion bending stiffness is at least 40 N*m. 2 The minimum torsional stiffness of the root portion is at least 20 N*m. 2 In another embodiment, the minimum root bending stiffness is at least 50 N*m. 2 The minimum torsional stiffness of the root portion is at least 30 N*m. 2 In a particularly unusual embodiment, the torsional stiffness of the minimum root portion is greater than the bending stiffness of the minimum root portion (compared to...). Figure 18 (Similar to the red tip in the image).

[0063] In one embodiment, this relationship is achieved by maintaining a shaft outer diameter that is at least 50% constant along the shaft length 130, thereby ensuring the preservation of this beneficial relationship. In yet another embodiment, the shaft outer diameter is constant for at least 75% along the shaft length 130. In another embodiment, the root portion outer diameter 1070 is constant along the entire root portion length 1030. In yet another embodiment, the proximal portion outer diameter 2070 is constant for at least 50% along the tip portion length 2030. And in yet another embodiment, it is constant for at least 75% along the tip portion length 2030.

[0064] This beneficial relationship can be further achieved and maintained by controlling the length of individual components. In one such embodiment, the tip length 2030 is no more than 55% of the root length 1030; in another embodiment, the tip length 2030 is at least 15% of the root length 1030; in yet another embodiment, the tip length 2030 is at least 4"; in another embodiment, it is at least 4-16"; and in yet another embodiment, it is at least 6-12". In yet another such embodiment, the root length 1030 is at least twice the tip length 2030; in another embodiment, the root length 1030 is at least three times the tip length 2030; in yet another embodiment, the root length 1030 is at least 2-5 times the tip length 2030; and in yet another embodiment, the root length 1030 is at least 2.5-4 times the tip length 2030. The root length 1030 is at least 16" in another embodiment, at least 20" in yet another embodiment, and at least 24" in yet another embodiment. Other embodiments limit the root portion length 1030 to no more than 48" in one embodiment, no more than 42" in another, no more than 36" in yet another, no more than 30" in yet another, and no more than 28" in yet another.

[0065] In yet another embodiment, the bending stiffness of the shaft is constant for at least 10% of the shaft length 130, and the torsional stiffness of the shaft is constant for at least 10% of the shaft length 130. In yet another embodiment, the bending stiffness of the shaft is constant for at least 25% of the shaft length 130, and the torsional stiffness of the shaft is constant for at least 25% of the shaft length 130. In yet another embodiment, the bending stiffness of the shaft is constant for at least 40% of the shaft length 130, and the torsional stiffness of the shaft is constant for at least 40% of the shaft length 130. In yet another embodiment, the bending stiffness of the shaft is constant for at least 50% of the shaft length 130, and the torsional stiffness of the shaft is constant for at least 50% of the shaft length 130. Similarly, in another embodiment, the range is defined as no more than 90% of the bending stiffness of the shaft and no more than 90% of the torsional stiffness of the shaft being constant along the shaft length 130. In another embodiment, the bending stiffness of the shaft remains constant at no more than 75% along the shaft length 130, and the torsional stiffness of the shaft remains constant at no more than 75% along the shaft length 130. In yet another embodiment, the bending stiffness of the shaft remains constant at no more than 60% along the shaft length 130, and the torsional stiffness of the shaft remains constant at no more than 60% along the shaft length 130.

[0066] These relationships can also be achieved by keeping the outer diameter of the tip portion 2070 no more than 60% smaller than the outer diameter of the maximum root portion 1070, and in another embodiment by having a connector 3000 with a connector mass not exceeding 15% of the shaft mass. Other mass relationships also achieve some advantages by controlling the mass of specific components. For example, in one embodiment, the connector mass is at least 5% of the shaft mass; in another embodiment, the root portion mass is 40%-70% of the shaft mass; and in yet another embodiment, the root portion mass is 45%-65% of the shaft mass. Similarly, in another embodiment, the tip portion 2000 has a tip portion mass not exceeding 85% of the root portion mass; in another embodiment, the tip portion does not exceed 75% of the root portion mass; and in yet another embodiment, the tip portion does not exceed 35%-75% of the root portion mass. The root portion mass preferably does not exceed 85 grams, in another embodiment does not exceed 75 grams, and in yet another embodiment does not exceed 65 grams. Another series of embodiments limits the lower range of root portion mass, in one embodiment the root portion mass is at least 40 grams, in another embodiment at least 50 grams, and in yet another embodiment at least 60 grams. The connector mass preferably does not exceed 25 grams, in another embodiment at least 20 grams, and in yet another embodiment at least 15 grams. Another series of embodiments limits the lower range of connector mass, in one embodiment at least 5 grams, in another embodiment at least 7.5 grams, and in yet another embodiment at least 10 grams. In one embodiment, the kit comprises at least two root portions 1000, wherein the difference in root portion mass is at least 10 grams, in another embodiment at least 15 grams, and in yet another embodiment at least 20 grams. Another series of embodiments limits the difference to no more than 50 grams, in another embodiment at least 40 grams, and in yet another embodiment at least 35 grams. Other kit embodiments provide the user with high adjustability and significant tactile variation, wherein the root portion mass difference is at least 50% of the heaviest tip portion mass, in another embodiment at least 75%, and in yet another embodiment at least 95%. A lighter heel option may be advantageous for older and younger users, while a heavier heel option may be beneficial for users with high swing speeds.

[0067] The connector 3000 is formed of a connector material having a connector material density, connector mass, connector elastic modulus, and connector shear modulus, and has (i) a connector bending stiffness and (ii) a connector torsional stiffness at each point along the connector length 3030. In one embodiment, at least a portion of the connector 3000 has a connector bending stiffness greater than the tip portion bending stiffness of a portion of the tip portion 2000, and at least a portion of the connector 3000 has a connector torsional stiffness greater than the tip portion torsional stiffness of a portion of the tip portion 2000. In another embodiment, at least a portion of the connector 3000 has a connector bending stiffness greater than the root portion bending stiffness of a portion of the root portion 1000, and at least a portion of the connector 3000 has a connector torsional stiffness greater than the root portion torsional stiffness of a portion of the root portion 1000. In another embodiment, at least a portion of the connector 3000 has a bending stiffness 75% greater than that of a portion of the tip portion 2000, and at least a portion of the connector 3000 has a torsional stiffness 75% greater than that of a portion of the tip portion 2000. In yet another embodiment, at least a portion of the connector 3000 has a bending stiffness 100%-500% greater than that of a portion of the tip portion 2000, and at least a portion of the connector 3000 has a torsional stiffness 100%-500% greater than that of a portion of the tip portion 2000. In another embodiment, at least a portion of the connector 3000 has a bending stiffness 200%-500% greater than that of a portion of the tip portion 2000, and at least a portion of the connector 3000 has a torsional stiffness 200%-500% greater than that of a portion of the tip portion 2000. Furthermore, in another embodiment, at least a portion of the connector 3000 has a bending stiffness 300-500% greater than that of a portion of the tip portion 2000, and at least a portion of the connector 3000 has a torsional stiffness 300-500% greater than that of a portion of the tip portion 2000.

[0068] The disclosed stiffness relationships can be obtained in several ways, one of which includes varying the root portion inner diameter 1060 along the root portion length 1030 to achieve the disclosed stiffness relationship of the reinforced region 2500, and / or a stiffness relationship associated with a first portion of the shaft 100 extending two-thirds of the shaft length 130 from the proximal end 120 and a second portion of the shaft 100 extending one-third of the shaft length 130 from the distal end 110. In another embodiment, reinforcing material can be embedded in the root portion sidewall 1040 to obtain any of these relationships without changing the root portion inner diameter 1060. In these embodiments, the reinforcing material can be a tube of high-stiffness material extending 360 degrees around the root portion 1000 cross-section, or it can be an insert located locally and not extending 360 degrees around the root portion 1000 cross-section.

[0069] In another embodiment, it may further include, as shown in Figure 3, Figure 4 The root insert 4000 shown in Figure 7(A) is attached to the root portion 1000 to obtain any of these relationships, and has a root insert distal end 4010, a root insert proximal end 4020, a root insert length 4030 of at least 25% of the tip portion length 2030, a root insert sidewall 4040 having a root insert sidewall thickness 4050, a root insert inner diameter 4060, and a root insert outer diameter 4070 smaller than the root insert inner diameter 1060, wherein the majority of the root insert length 4030 is within the reinforcing region 2500. In another embodiment, the root portion insert length 4030 is at least 50% and no more than 50% of the tip portion length 2030, while in yet another embodiment, the root portion insert length 4030 is at least 10% and no more than 150% of the tip portion length 2030, and in still another embodiment, the root portion insert inner diameter 4060 is larger than the tip portion inner diameter 2060. In yet another embodiment, at least 75% of the root portion insert length 4030 is within the reinforcing region 2500, while in another embodiment, the entire root portion insert 4000 is within the reinforcing region 2500. Figure 4 As shown, in another embodiment, the proximal end 4020 of the root insert is separated from the distal end 3010 of the connector by a separation distance 4080 of at least 50% of the outer diameter 1070 of the root portion, thereby achieving the disclosed stiffness difference between the root insert 4000 and the connector 3000. In one such embodiment, the separation distance 4080 does not exceed five times the outer diameter 1070 of the root portion, while in another embodiment, the separation distance 4080 does not exceed 50% of the length 4030 of the root insert.

[0070] In one embodiment, the root insert length 4030 is at least 2"; in another embodiment, it is at least 4"; and in yet another embodiment, it is at least 6". However, additional embodiments limit the root insert length 4030 so as not to impair the advantages associated with the root insert 4000. Specifically, in one embodiment, the root insert length 4030 does not exceed 12"; in another embodiment, it does not exceed 10"; and in yet another embodiment, it does not exceed 8". Additionally, the placement of the root insert 4000 is essential to providing the described advantages. In one specific embodiment, the distance from the proximal end 4020 of the root insert to the proximal end 120 of the shaft is at least 7"; in another embodiment, at least 9"; and in yet another embodiment, at least 11". Additional embodiments reduce the likelihood of compromising the advantages associated with the root insert 4000 by controlling this distance. For example, in one embodiment, the distance from the proximal end 4020 of the root insert to the proximal end 120 of the shaft is no more than 18"; in another embodiment, no more than 16"; and in yet another embodiment, no more than 14".

[0071] Those skilled in the art will understand that the root insert 4000 has a center of gravity (CG), and the position of the root insert CG significantly affects the advantage associated with the golf club shaft 100. In one such embodiment, the root insert CG is located at least 9" from the proximal end 120 of the shaft, at least 11" in another embodiment, and at least 13" in yet another embodiment. In some embodiments, a detriment to the advantage associated with the root insert 4000 has been observed when the distance from the proximal end 120 of the shaft becomes too large. Therefore, in another embodiment, the root insert CG is located no more than 19" from the proximal end 120 of the shaft, no more than 17" in another embodiment, and no more than 15" in yet another embodiment. In another embodiment, the separation distance from the shaft CG to the root insert CG is less than the root insert length 4030, in another embodiment no more than 75% of the root insert length 4030, and in yet another embodiment no more than 50% of the root insert length 4030. In another variation, the second separation distance is defined as the distance from the inflection point (defined later) to the position of the root insert CG when it is mounted on the shaft. This second separation distance is less than the root insert length 4030, and in another embodiment, does not exceed 75% of the root insert length 4030. In yet another embodiment, it does not exceed 50% of the root insert length 4030. Therefore, in one embodiment, when the insert is mounted on the shaft, the positions of the shaft CG and the inflection point both fall between the distal end 4010 and the proximal end 4020 of the root insert.

[0072] The root insert 4000 is formed of a root insert material having a root insert material density, a root insert mass, a root insert elastic modulus, and a root insert shear modulus. At each point along the root insert length 4030, it has (i) a root insert bending stiffness and (ii) a root insert torsional stiffness. In one embodiment, at least a portion of the root insert 4000 has a root insert bending stiffness greater than that of a portion of the tip portion 2000, and at least a portion of the root insert 4000 has a root insert torsional stiffness greater than that of a portion of the tip portion 2000. In another embodiment, at least a portion of the root insert 4000 has a root insert bending stiffness greater than that of a portion of the root portion 1000, and at least a portion of the root insert 4000 has a root insert torsional stiffness greater than that of a portion of the root portion 1000. In yet another embodiment, at least a portion of the root insert 4000 has a root insert bending stiffness that is 75% greater than the tip portion bending stiffness of a portion of the tip portion 2000, and at least a portion of the root insert 4000 has a root insert torsional stiffness that is 75% greater than the tip portion torsional stiffness of a portion of the tip portion 2000. In yet another embodiment, at least a portion of the root insert 4000 has a root insert bending stiffness that is 100%-300% greater than the tip portion bending stiffness of a portion of the tip portion 2000, and at least a portion of the root insert 4000 has a root insert torsional stiffness that is 100%-300% greater than the tip portion torsional stiffness of a portion of the tip portion 2000.

[0073] As shown in Figure 7(B), the root insert 4000 may be a hollow tubular structure that may include at least one structural support spanning the interior of the root insert 4000 and passing through its center. In another embodiment, the length of the structural support extending into and out of the page in Figure 7(B) is at least 1 / 16", in another embodiment at least 1 / 8", and in yet another embodiment at least 1 / 4". In the embodiment of Figure 7(A), the length of the structural support is at least 50% of the root insert length 4030, in another embodiment it is at least 75% of the root insert length 4030, and in yet another embodiment it is at least 90% of the root insert length 4030.

[0074] Another embodiment includes at least two structural supports that span the interior of the root insert 4000, pass through it, and intersect at its center, while another embodiment includes at least three. The root insert sidewall thickness 4050 preferably does not exceed the root insert sidewall thickness 1050, while in another embodiment, the root insert sidewall thickness 4050 preferably does not exceed 75% of the root insert sidewall thickness 1050, and in yet another embodiment, the root insert sidewall thickness 4050 preferably does not exceed 50% of the root insert sidewall thickness 1050. In yet another series of embodiments, the root insert sidewall thickness 4050 is at least 50% of the tip insert sidewall thickness 2050, while in another embodiment, the root insert sidewall thickness 4050 is preferably at least 75% of the tip insert sidewall thickness 2050, and in yet another embodiment, the root insert sidewall thickness 4050 is preferably at least 100% of the tip insert sidewall thickness 2050. In one embodiment, the root portion insert 4000 is formed of a metallic material, while in another embodiment it is formed of a metallic material different from that of the tip portion 2000, and in yet another embodiment it is formed of a metallic material with a density at least 35% less than that of the tip portion 2000.

[0075] These relationships result in less clubface distortion before, during, and after impact, and improve the consistency of clubface speed with heel and toe acceleration. Figure 13(A) shows the toe and heel speeds of the Anser putter head during the swing under eccentric effects, attached to a conventional steel putter shaft for a robot, while Figure 14(A) shows an embodiment of the same putter head attached to a golf club 1000. The intersection of the heel and toe lines in Figure 13(A) indicates instability in the putter head, while Figure 14(A) shows the improved performance of the golf club shaft 1000 where the heel and toe lines do not intersect.

[0076] Similarly, Figure 13(B) shows the acceleration of the toe and heel of the same Anser putter head during the swing under the influence of eccentricity, attached to a conventional steel putter shaft attached to a robot, while Figure 14(B) shows an embodiment of the same putter head attached to a golf club shaft 1000. The difference between the heel and toe lines in Figure 13(A) illustrates the instability of the putter head, while the difference in Figure 14(B) shows the improved performance of the golf club shaft 1000, where the difference between the heel and toe lines is significantly reduced. These improvements demonstrate enhanced stability, resulting in improved ball roll characteristics, a lower launch angle, and less dispersion. These relationships can significantly improve the relative fluctuations in velocity and acceleration of the toe and heel of the clubface before, during, and after impact, without reducing the feel at impact and after impact.

[0077] Any of these embodiments may further establish a third portion of the reinforced region 2500, wherein the shaft bending stiffness is greater than that of the first portion and less than that of the second portion, and the shaft torsional stiffness is greater than that of the first portion and less than that of the second portion. In yet another embodiment, the third portion of the reinforced region 2500 has a shaft bending stiffness that is at least 25% greater than that of the first portion and at least 25% less than that of the second portion, and a shaft torsional stiffness that is at least 25% greater than that of the first portion and at least 25% less than that of the second portion. In one embodiment, the root insert 4000 has a root insert mass that is at least 10% of the shaft mass, while in another embodiment, the root insert mass does not exceed 25% of the shaft mass.

[0078] In one embodiment, the connector 3000 is formed of a metallic connector material, the density of which is less than the density of the tip material but at least 15% greater than the density of the root material. In another embodiment, the tip material density is at least 50% greater than the root material density; in yet another embodiment, the tip material density is at least twice the density of the connector material; and in still another embodiment, the tip material density is no more than six times the density of the root material. In one specific embodiment, the tip material density is at least 7 g / cc, the connector material density is 2.5-5.0 g / cc, and the root material density is no more than 2.4 g / cc. In another embodiment, the root material density and / or the tip material density is no more than 2.0 g / cc; in another embodiment, no more than 1.8 g / cc; and in yet another embodiment, no more than 1.6 g / cc. The elastic modulus of the tip material is preferably at least 110 GPa, and its shear modulus is preferably at least 40 GPa; in yet another embodiment, the elastic modulus of the tip material is preferably at least 190 GPa, and its shear modulus is preferably at least 70 GPa. The elastic modulus of the connector material is preferably at least 60 GPa, and its shear modulus is preferably at least 20 GPa. In another embodiment, the elastic modulus of the connector material is preferably at least 110 GPa, and its shear modulus is preferably at least 40 GPa. The elastic modulus of the root material is preferably at least 40 GPa, and its shear modulus is preferably at least 15 GPa. In another embodiment, the elastic modulus of the root material is preferably at least 50 GPa, and its shear modulus is preferably at least 22.5 GPa. This also applies to embodiments of the non-metallic tip portion. The materials of the root portion 1000, the tip portion 2000, and / or the connector 3000 may include metal alloys (e.g., titanium alloys, steel alloys, aluminum alloys, and / or magnesium alloys), composite materials (e.g., graphite composites, ceramic materials, fiber-reinforced composites, molded composites used to form a compression molded body that may include multiple randomly oriented carbon fiber bundles), thermoset or thermoplastic matrix materials, plastics, or any combination thereof. In one embodiment, carbon fibers may account for 10%-70% of the volume of the composite material. In another embodiment, the method of forming a composite component includes: setting a plurality of carbon fiber bundles; mixing the bundles with a matrix material such that the bundles are randomly sorted to form a composite molding material; setting male and female metal tooling molds; placing the composite molding material in the female metal tooling mold; pressing the composite molding material in the female metal tooling mold using the male metal tooling mold to generate a composite workpiece; and allowing the composite workpiece to cure, wherein each carbon fiber bundle is unidirectional, and wherein each bundle includes no more than 12,000 carbon fibers. In another embodiment, each bundle includes no more than 3,000 carbon fibers. The matrix material used may be a thermosetting material, more preferably, vinyl ester or epoxy resin. Further, the carbon fiber lengths used in this embodiment may be between 1 / 4 inch and 2 inches.

[0079] As shown in Figures 8(A) and 8(B), the connector 3000 may have a connector-root insert portion 3100 and a connector-tip receiving portion 3200, which in some embodiments are separated by a variation in the connector outer diameter 3070, which forms a flange having a flange height not greater than the root portion sidewall thickness 1050. The connector-root insert portion 3100 has a connector-root insert distal end 3110, a connector-root insert proximal end 3120, a connector-root insert length 3130 between the connector-root insert distal end 3110 and the connector-root insert proximal end 3120, a connector-root insert sidewall 3140, a connector-root insert sidewall thickness 3150, a connector-root insert inner diameter 3160, and a connector-root insert outer diameter 3170. Similarly, the connector-tip receiving portion 3200 has a connector-tip receiving distal end 3210, a connector-tip receiving proximal end 3220, a connector-tip receiving length 3230 between the connector-tip receiving distal end 3210 and the connector-tip receiving proximal end 3220, a connector-tip receiving sidewall 3240, a connector-tip receiving sidewall thickness 3250, and a connector-tip receiving inner diameter 3260. In one embodiment, the connector-root insert outer diameter 3170 does not exceed the root portion inner diameter 1060, while in another embodiment, the connector-tip receiving inner diameter 3260 is at least as large as the tip portion outer diameter 2070. The connector-tip receiving length 3230 is preferably greater than the tip portion outer diameter 2070, and the connector-root insert length 3130 is preferably greater than the root portion inner diameter 1060. In another embodiment, the connector-root insert length 3130 is at least 50% larger than the connector-tip receiving length 3230, at least 75% larger in another embodiment, and at least 100% larger in yet another embodiment. Alternatively, those skilled in the art will understand that the connector 3000 can be configured in the opposite manner, wherein a portion of the root portion 1000 is received within a portion of the connector 3000, and a portion of the connector 3000 is received within a portion of the tip portion 2000. Alternatively, in another embodiment, a portion of the connector 3000 is received within both a portion of the root portion 1000 and a portion of the tip portion 2000. Alternatively, in yet another embodiment, both a portion of the root portion 1000 and a portion of the tip portion 2000 are received within a portion of the connector 3000.

[0080] The connector sidewall thickness 3050 preferably does not exceed the root portion sidewall thickness 1050, and in one embodiment, the connector sidewall thickness 3050 is at least 10% smaller than the root portion sidewall thickness 1050. In another embodiment, a portion of the connector sidewall 3040 has a varying connector sidewall thickness 3050; in yet another embodiment, the varying thickness is the connector-tip receiving sidewall thickness 3250; and in still another embodiment, the connector-tip receiving sidewall thickness 3250 varies between a minimum and a maximum value, wherein the maximum value is at least 50% greater than the minimum value. In yet another embodiment, the maximum connector-tip receiving sidewall thickness 3250 is at least 50% greater than the connector-root insert sidewall thickness 3150.

[0081] In the illustrated embodiment, the tip portion 2000 extends through the connector-tip receiving portion 3200 and into the connector-root insert portion 3100 such that the cross-section of a portion of the entire shaft 100 includes the outer root portion 1000, the middle connector 3000, and the inner tip portion 2000, thereby achieving the relationship described herein. In another embodiment, the distal end 2010 of the tip portion extends a first distance of at least 50% of the outer diameter 1070 of the root portion in the connector-root insert portion 3100, in another embodiment at least 75%, and in yet another embodiment at least 100%. Another series of embodiments limits this first distance to no more than 50% of the tip portion length 2030 and no more than 10 times the outer diameter 1070 of the root portion; in another embodiment, the first distance is no more than 35% of the tip portion length 2030 and no more than 6 times the outer diameter 1070 of the root portion; and in yet another embodiment, the first distance is no more than 25% of the tip portion length 2030 and no more than 4 times the outer diameter 1070 of the root portion. The embodiment of Figure 8(A) includes an opening on the distal end 3010 of the connector that allows air to pass through. In one embodiment, the open area of ​​the opening is at least 10% of the area associated with the outer diameter 3070 of the connector, in another embodiment at least 20%, and in yet another embodiment at least 30%.

[0082] The shaft 100 of any disclosed embodiment may be further attached to the golf club head 5000 and includes a grip 6000 attached to the distal end 110 of the shaft, thereby creating a golf club suitable for use. Those skilled in the art will understand that the golf club can be a putter, driver, fairway wood, hybrid or rescue club, iron, and / or wedge iron. In one specific embodiment, the golf club is a putter with a loft angle of less than 10 degrees; in another embodiment, its head mass is at least 310 grams; in yet another embodiment, the shaft length 130 does not exceed 36"; in yet another embodiment, the head mass is at least 320 grams; in yet another embodiment, at least 330 grams; and in yet another embodiment, at least 340 grams.

[0083] The shaft 100 can be a putter shaft, a wedge iron shaft, an iron shaft, a rescue shaft, a fairway wood shaft, and / or a driver shaft. In one specific putter shaft embodiment, the shaft length 130 does not exceed 38" and the shaft weight is at least 100 grams; in another embodiment, the shaft length 130 does not exceed 36" and the shaft weight is 100-150 grams; and in yet another embodiment, the shaft length 130 does not exceed 35" and the shaft weight is 110-140 grams. In one embodiment, the tip portion 2000 is straight; in another embodiment for some putters, the tip portion 2000 includes a double bend, as will be understood by those skilled in the art. Those skilled in the art will understand that the entire… Each shaft 100 will have a shaft center of gravity CG, the position of which can be referenced as a shaft CG distance of 120 from the near end of the shaft. In a putter embodiment with a shaft length 130 of less than 35.5", the advantages described herein are enhanced when the shaft CG distance is no more than 18", in another embodiment, no more than 17", and in yet another embodiment, no more than 16". Further, the advantages described herein are enhanced when the shaft CG distance is at least 9", in another embodiment, at least 11", and in yet another embodiment, at least 13". In one specific embodiment, the shaft CG distance is 13"-15.5". In another embodiment, these shaft CG distances are obtained using a shaft length 130 not exceeding 35"; in another embodiment, the shaft length 130 does not exceed 34"; and in yet another embodiment, the shaft length 130 does not exceed 33". In more embodiments, the shaft CG distance does not exceed 45% of the shaft length 130; in another embodiment, it does not exceed 40% of the shaft length 130; and in yet another embodiment, it does not exceed 35% of the shaft length 130. However, in yet another series of embodiments, the shaft CG distance is at least 20% of the shaft length 130; in another embodiment, it is at least 25% of the shaft length 130; and in yet another embodiment, it is at least 30% of the shaft length 130.

[0084] A typical 35" tapered steel putter shaft has a shaft CG distance of approximately 20" and a turnout distance of approximately 14". The turnout distance of the golf club shaft is determined by applying an axial compressive load to the shaft tip or near end 120 until the distance between the two ends changes by 0.5" after fixing the shaft heel or distal end 110. The point of maximum deflection is then identified as the location of the maximum deflection relative to the initial shaft axis. The turnout distance is the distance along the initial shaft axis from the near end 120 to the point of maximum deflection.

[0085] As the shaft CG distance decreases, surprising performance advantages are discovered, with increased inflection point distance and a decrease in the combination of shaft CG distance and inflection point distance, or the difference between them. In one embodiment of the invention, the inflection point distance is at least 75% of the shaft CG distance; in another embodiment, at least 85%; in yet another embodiment, at least 95%; and in still another embodiment, at least 105%. In another series of embodiments, the inflection point distance does not exceed 14% of the shaft CG distance; in another embodiment, it does not exceed 135%; in yet another embodiment, it does not exceed 125%; and in yet another embodiment, it does not exceed 115%. In a particularly effective embodiment, the inflection point distance is at least 85%-135% of the shaft CG distance; in another embodiment, at least 95%-125%; and in yet another embodiment, at least 100%-115%. In another embodiment of the invention, the shaft CG distance does not exceed 50% of the shaft length 130; in another embodiment, it does not exceed 47.5%; in yet another embodiment, it does not exceed 45%; and in yet another embodiment, it does not exceed 42.5%. In another series of embodiments, the shaft CG distance is at least 30% of the shaft length 130, at least 35% in another embodiment, at least 37.5% in yet another embodiment, and at least 40% in yet another embodiment.

[0086] The difference between the shaft CG distance and the inflection point distance preferably does not exceed 12.5% ​​of the shaft length 130", in another embodiment does not exceed 10%, in yet another embodiment does not exceed 7.5%, and in still another embodiment does not exceed 5%. In a particularly effective embodiment, the difference between the shaft CG distance and the inflection point distance preferably does not exceed 4.5", in another embodiment does not exceed 3.5", in yet another embodiment does not exceed 2.5", and in still another embodiment does not exceed 1.5". In one embodiment, the shaft CG distance does not exceed 18.0", in another embodiment does not exceed 16.0", in yet another embodiment does not exceed 15.5", and in still another embodiment does not exceed 15.0", wherein the shaft length is 35.0".

[0087] In one embodiment, the outer diameter of the root portion 1070 is 0.500-0.700", while in another embodiment, the outer diameter of the root portion 1070 is 0.550-0.650", and in yet another embodiment, the outer diameter of the root portion 1070 is 0.580-0.620". In another embodiment, the outer diameter of the tip portion 2070 is 0.300-0.450", while in another embodiment, the outer diameter of the tip portion 2070 is 0.330-0.420", and in yet another embodiment, the outer diameter of the tip portion 2070 is 0.350-0.390".

[0088] The “part” disclosed herein as a “part” of a first component having a first stiffness relative to a second component having a different second stiffness includes another embodiment in which the relationship is true over at least 25% of the length of the first component and / or at least 25% of the length of the second component, or in another embodiment in which the relationship is true over at least 50% of the length of the first component and / or at least 50% of the length of the second component, and in yet another embodiment in which the relationship is true over at least 75% of the length of the first component and / or at least 75% of the length of the second component.

[0089] Now back Figures 9 to 12 The abbreviations EI and GJ refer to the bending stiffness and torsional stiffness of the shaft, respectively. As mentioned above, the bending stiffness and torsional stiffness of the shaft are the bending stiffness and torsional stiffness of the shaft at various points along the shaft length 100, perpendicular to the shaft axis. This takes into account the region of shaft 100 composed of multiple components within a specific cross-section. In other regions of shaft 100 where no independent components overlap, the shaft stiffness is equal to the stiffness of the single component present at that specific location on the cross-section. Now, let's refer to... Figure 9Starting from the left boundary of the figure, the bending stiffness (EI) and torsional stiffness (GJ) of the shaft 100, which only includes a portion of the tip portion 2000 with a constant cross-sectional distribution in this embodiment, are constant, i.e., horizontal along the first bending stiffness stabilization period and the first torsional stiffness stabilization period. Subsequently, the bending stiffness rises along the first bending stiffness to the second bending stiffness stabilization period, while the torsional stiffness rises along the first torsional stiffness to the second torsional stiffness stabilization period. In this embodiment, the rise begins at the point where the tip portion 2000 enters the connector-tip receiving portion 3200 of the connector 3000, see Figure 8(A), taking into account overlap and the increased connector-tip receiving sidewall thickness 3250. In this embodiment, the second bending stiffness stabilization period and the second torsional stiffness stabilization period represent constant stiffness regions because they are regions along the length 130 of the rod, including the root portion 1000 overlapping with the connector-root insert portion 3100 of the connector 3000, and they have a constant cross-sectional distribution in this embodiment. In this embodiment, as Figure 4 The shown rod 100 only includes the region of the root portion 1000 within the separation distance 4080, where the stiffness subsequently drops to the third bending stiffness stabilization period and the third torsional stiffness stabilization period. In this embodiment, this region has a constant cross-sectional distribution. In this embodiment, as... Figure 4 In the region of the shaft 100 shown, including the root portion 1000 and the root portion insert 4000, the stiffness increases to the fourth bending stiffness stabilization period and the fourth torsional stiffness stabilization period. In this embodiment, this region has a constant cross-sectional distribution. In this embodiment, in the region of the shaft 100 containing only the root portion 1000, the stiffness decreases to the fifth bending stiffness stabilization period and the fifth torsional stiffness stabilization period. In this embodiment, this region also has a constant cross-sectional distribution. In one embodiment, the stabilization periods described herein are not constant but have a positive or negative slope not exceeding 10 degrees, much smaller than the variations found in conventional tapered or stepped shafts, for example... Figure 12 As shown in the illustration. In another embodiment, the positive or negative slope does not exceed 7.5 degrees; in yet another embodiment, the positive or negative slope does not exceed 5 degrees; and in still another embodiment, the positive or negative slope does not exceed 2.5 degrees.

[0090] like Figure 9As shown in the chart, the average flexural stiffness of the second stable period is at least twice that of the average flexural stiffness of the first stable period. In another embodiment, the average flexural stiffness of the second stable period is at least 50% greater than the average flexural stiffness of the third stable period. In yet another embodiment, the average flexural stiffness of the second stable period is at least 25% greater than the average flexural stiffness of the fourth stable period. In still another embodiment, the average flexural stiffness of the second stable period is at least 50% greater than the average flexural stiffness of the fifth stable period. Similarly, the average torsional stiffness of the second stable period is at least twice that of the average torsional stiffness of the first stable period. In another embodiment, the average torsional stiffness of the second stable period is at least 50% greater than the average torsional stiffness of the third stable period. In yet another embodiment, the average torsional stiffness of the second stable period is at least 25% greater than the average torsional stiffness of the fourth stable period. In another embodiment, the average torsional stiffness of the second stable period is at least 50% greater than the average torsional stiffness of the fifth stable period of the third stable period.

[0091] In another embodiment, the average fourth-steady-state bending stiffness of the fourth-steady-state period is at least 10% greater than the average steady-state bending stiffness of the adjacent steady-state periods, wherein in one embodiment the adjacent steady-state periods are oriented towards the distal end 120 of the shaft, and in another embodiment the adjacent steady-state periods are oriented towards the proximal end 110 of the shaft. Similarly, in another embodiment, the average fourth-steady-state torsional stiffness of the fourth-steady-state period is at least 10% greater than the average steady-state torsional stiffness of the adjacent steady-state periods, wherein in one embodiment the adjacent steady-state periods are oriented towards the distal end 120 of the shaft, and in another embodiment the adjacent steady-state periods are oriented towards the proximal end 110 of the shaft.

[0092] In another embodiment, the average third-stabilized bending stiffness of the third stabilized period is at least 10% smaller than the average stabilized bending stiffness of the adjacent stabilized periods, wherein in one embodiment the adjacent stabilized periods are oriented towards the distal end 120 of the shaft, and in another embodiment the adjacent stabilized periods are oriented towards the proximal end 110 of the shaft. Similarly, in another embodiment, the average third-stabilized torsional stiffness of the third stabilized period is at least 10% smaller than the average stabilized torsional stiffness of the adjacent stabilized periods, wherein in one embodiment the adjacent stabilized periods are oriented towards the distal end 120 of the shaft, and in another embodiment the adjacent stabilized periods are oriented towards the proximal end 110 of the shaft.

[0093] In another embodiment, the average second-stabilized bending stiffness of the second stabilized period is at least 50% greater than the average stabilized bending stiffness of the adjacent stabilized periods, wherein in one embodiment the adjacent stabilized periods are oriented towards the distal end 120 of the shaft, and in another embodiment the adjacent stabilized periods are oriented towards the proximal end 110 of the shaft. Similarly, in another embodiment, the average second-stabilized torsional stiffness of the second stabilized period is at least 50% greater than the average stabilized torsional stiffness of the adjacent stabilized periods, wherein in one embodiment the adjacent stabilized periods are oriented towards the distal end 120 of the shaft, and in another embodiment the adjacent stabilized periods are oriented towards the proximal end 110 of the shaft.

[0094] In one embodiment, the third stabilization period has a shaft bending stiffness that is (a) at least 50% greater than the tip bending stiffness, i.e., the first stabilization period bending stiffness, and (b) less than 100 N*m. 2 Similarly, the third stabilization period has a shaft torsional stiffness that is (a) at least 50% greater than the tip torsional stiffness, i.e., the first stabilization period torsional stiffness, and (b) less than 100 N*m. 2 In another embodiment, the second stabilization period has a shaft bending stiffness that is (a) at least 50% greater than the root bending stiffness, i.e., the bending stiffness of the third or fifth stabilization period, and (b) greater than 120 N*m. 2 Similarly, the second stabilization period has a shaft torsional stiffness that is (a) at least 50% greater than the root torsional stiffness, i.e., the torsional stiffness of the third or fifth stabilization period, and (b) greater than 120 N*m. 2 .

[0095] In another embodiment, a portion of the fourth stabilization period is located within the reinforced region 2500 and has a shaft bending stiffness that is (a) greater than the shaft bending stiffness of the third stabilization period and (b) less than the shaft bending stiffness of the second stabilization period. Similarly, in another embodiment, a portion of the fourth stabilization period is located within the reinforced region 2500 and has a shaft torsional stiffness that is (a) greater than the shaft torsional stiffness of the third stabilization period and (b) less than the shaft torsional stiffness of the second stabilization period.

[0096] In another embodiment, both the bending stiffness distribution and the torsional stiffness distribution of the shaft include at least four distinct stabilization periods, each with a length of at least 2" and at least one stabilization period with a length of at least 6". In another embodiment, both the bending stiffness distribution and the torsional stiffness distribution of the shaft include at least five distinct stabilization periods, each with a length of at least 2" and at least two stabilization periods with a length of at least 6" and at least one stabilization period with a length of at least 10".

[0097] exist Figure 10In diagram (A), the shaft 100 is divided into a tip region and a root region, which separate at the midpoint of the shaft length 130. Therefore, the region from the midpoint to the near end 120 of the shaft is the tip region, while the region from the midpoint to the far end 110 of the shaft is the root region. In one embodiment, the average bending stiffness of the tip region is within 25% of the average bending stiffness of the root region, while... Figure 12 As shown, the average tip region bending stiffness of a conventional tapered or stepped shaft is less than 40% of the average root region bending stiffness. In another embodiment, the average tip region bending stiffness is within 15% of the average root region bending stiffness, in yet another embodiment within 10%, and in still another embodiment within 5%. In one specific embodiment, the average tip region bending stiffness is at least as large as the average root region bending stiffness. Similarly, in one embodiment, the average tip region torsional stiffness is within 25% of the average root region torsional stiffness, while... Figure 12 As shown, the average torsional stiffness of the tip region of a conventional tapered or stepped shaft is less than 40% of the average torsional stiffness of the root region. In another embodiment, the average torsional stiffness of the tip region is within 15% of the average torsional stiffness of the root region; in yet another embodiment, it is within 10%; and in still another embodiment, it is within 5%.

[0098] exist Figure 10 In diagram (B), the shaft 100 is divided into a tip non-reinforced region, a reinforced region, and a root non-reinforced region. All the above disclosures and embodiments of the reinforced region 2500 are applicable. Figure 10The reinforced region 2500 has an average reinforced region bending stiffness and an average reinforced region torsional stiffness. The tip-unreinforced region has an average tip-unreinforced region bending stiffness and an average tip-unreinforced region torsional stiffness, and the root-unreinforced region has an average root-unreinforced region bending stiffness and an average root-unreinforced region torsional stiffness. The average of the average tip-unreinforced region bending stiffness and the average root-unreinforced region bending stiffness is the average unreinforced region bending stiffness. Similarly, the average of the average tip-unreinforced region torsional stiffness and the average root-unreinforced region torsional stiffness is the average unreinforced region torsional stiffness. In one embodiment, the average reinforced region bending stiffness is at least 50% greater than the average unreinforced region bending stiffness; in another embodiment, it is at least 60% greater; and in yet another embodiment, it is at least 70% greater. Similarly, in another embodiment, the average reinforced region torsional stiffness is at least 40% greater than the average unreinforced region torsional stiffness; in another embodiment, it is at least 50% greater; and in yet another embodiment, it is at least 60% greater. In yet another embodiment, the average flexural stiffness of the reinforced region is 50%-150% greater than that of the average unreinforced region, 60-125% greater in another embodiment, and 65-100% greater in yet another embodiment. Similarly, in another embodiment, the average torsional stiffness of the reinforced region is 40%-120% greater than that of the average unreinforced region, 50%-110% greater in another embodiment, and 55%-100% greater in yet another embodiment.

[0099] exist Figure 11 In diagram (D), the shaft 100 is divided into a tip two-thirds region and a root one-third region based on the shaft length 130. The first portion of the shaft 100 extending two-thirds of the shaft length 130 from the near end 120 (i.e., the tip two-thirds region) has a first average bending stiffness, and the second portion of the shaft 100 extending one-third of the shaft length 130 from the far end 110 (i.e., the root one-third region) has a second average bending stiffness, with the first average bending stiffness being at least 50% of the second average bending stiffness. These relationships differ significantly from those found in conventional tapered or stepped shafts, where the tip two-thirds region has less than 42% of the average bending stiffness of the root one-third region, such as... Figure 12 As shown. Similarly, the tip two-thirds region has a first average torsional stiffness, and the root one-third region has a second average torsional stiffness, with the first average torsional stiffness being at least 50% of the second average torsional stiffness. These relationships differ significantly from those found in conventional tapered or stepped shafts, where the tip two-thirds region has an average torsional stiffness that is at least 42% less than that of the root one-third region, such as... Figure 12As shown. In another embodiment, the first average bending stiffness is at least 75% of the second average bending stiffness. In another related embodiment, the first average bending stiffness is at least 100% of the second average bending stiffness, while in yet another related embodiment, the first average bending stiffness is 75%-200% of the second average bending stiffness, and in still another related embodiment, the first average bending stiffness is 100%-150% of the second average bending stiffness. In another embodiment, the first average torsional stiffness is at least 75% of the second average torsional stiffness. In another related embodiment, the first average torsional stiffness is at least 100% of the second average torsional stiffness, while in yet another related embodiment, the first average torsional stiffness is 75%-200% of the second average torsional stiffness, and in still another related embodiment, the first average torsional stiffness is 100%-150% of the second average torsional stiffness.

[0100] exist Figure 11 In diagram (C), the shaft 100 is divided into a tip third region and a root two-thirds region based on the shaft length 130. The first portion of the shaft 100 extending one-third of its length 130 from the near end 120 (i.e., the tip third region) has a tip third average bending stiffness, and the second portion of the shaft 100 extending two-thirds of its length 130 from the far end 110 (i.e., the root two-thirds region) has a root two-thirds average bending stiffness, with the tip third average bending stiffness being at least 50% of the root two-thirds average bending stiffness. These relationships differ significantly from those found in conventional tapered or stepped shafts, where the tip third region has an average bending stiffness that is at least 36% less than the root two-thirds average bending stiffness. Figure 12 As shown. Similarly, the tip third region has the tip third average torsional stiffness, the root two-thirds region has the root two-thirds average torsional stiffness, and the tip third average torsional stiffness is at least 50% of the root two-thirds average torsional stiffness. These relationships differ significantly from those found in conventional tapered or stepped shafts, where the tip third region has an average torsional stiffness that is at least 36% less than the root two-thirds average torsional stiffness, such as... Figure 12As shown. In another embodiment, the average bending stiffness of the tip third is at least 60% of the average bending stiffness of the root two-thirds. In another related embodiment, the average bending stiffness of the tip third is at least 70% of the average bending stiffness of the root two-thirds, and in yet another related embodiment, the average bending stiffness of the tip third is 60%-120% of the average bending stiffness of the root two-thirds, and in yet another related embodiment, the average bending stiffness of the tip third is 70%-110% of the average bending stiffness of the root two-thirds. In another embodiment, the average torsional stiffness of the tip third is at least 60% of the average torsional stiffness of the root two-thirds. In another related embodiment, the average torsional stiffness of the tip third is at least 70% of the average torsional stiffness of the root two-thirds, and in yet another related embodiment, the average torsional stiffness of the tip third is 60%-120% of the average torsional stiffness of the root two-thirds, and in yet another related embodiment, the average torsional stiffness of the tip third is 70%-110% of the average torsional stiffness of the root two-thirds.

[0101] like Figure 15 As shown, the connector 3000 can be configured to releasably engage the root portion 1000 and the tip portion 2000. The releasability of the connector 3000 allows (a) a single tip portion 2001 to engage with a plurality of root portions (1001, 1002, 1003, 1004) having different characteristics, thereby identifying the optimal combination for a specific golfer; (b) a single root portion 1001 to engage with a plurality of tip portions (2001, 2002, 2003, 2004) having different characteristics, thereby identifying the optimal combination for a specific golfer; and / or (c) any other such combination. Generally, for ease of explanation, the invention focuses on kits or systems comprising a single root portion 1001 mating with at least two different tip portions (2001, 2002). However, those skilled in the art will understand that the kit may include any number of root portions (1001, 1002, 1003, 1004) and tip portions (2001, 2002, 2003, 2004) engaged by a common universal connector 3001; however, it may also include multiple connectors (3001, 3002, 3003, 3004), thereby providing further options and stiffness characteristics as described herein. Furthermore, the unique stiffness characteristics and relationships disclosed herein are not limited to kits or releasable connectors, but may be incorporated into a single shaft or a shaft composed of multiple parts, whether directly joined together or joined by connectors, and whether a permanent connector construction or a releasable connector construction. Thus, regardless of the number of parts formed by the shaft 100, the shaft 100 has a distal shaft end 110, a proximal shaft end 120, a shaft outer diameter, a shaft length 130, and a shaft mass, as previously disclosed in detail and in Figure 16As shown in the figure. Each point along the shaft length 130 has shaft bending stiffness and shaft torsional stiffness. When referring to the root portion or root segment 1000 and the tip portion or tip segment 2000, the terms "portion" and "segment" are used interchangeably in this disclosure.

[0102] In some embodiments, the shaft 100 has a root portion (1000, 1001, 1002, 1003, 1004) of the tip portion 2000, which is releasably engaged by a connector (3000, 3001, 3002, 3003) to at least one of the first tip portion 2001 and the second tip portion 2002, but may also include a third tip portion 2003 or even a fourth tip portion 2004. As described in detail above, the root portion 1000 has a distal end 1010, a proximal end 1020, a length 1030, a sidewall 1040 having a sidewall thickness 1050, an inner diameter 1060, and an outer diameter 1070. Similarly, each tip portion has the following properties, which will not be repeated for each portion for the sake of brevity, but will be understood by those skilled in the art. The attributes include the distal end of the tip portion 2021, the proximal end of the tip portion 2020, the length of the tip portion 2030, the sidewall of the tip portion 2040 having a sidewall thickness of 2050, the inner diameter of the tip portion 2060 (in the case where the tip portion 2000 is hollow (but in some embodiments, the tip portion 2000 may be partially or entirely solid)), the outer diameter of the tip portion 2060, and the mass of the tip portion.

[0103] When multiple tip sections 2000 and / or multiple root sections 1000 are set as part of a kit, the properties just described do not need to be the same for each tip section or root section. In fact, one or more variations of the properties are desirable, although certain relationships are particularly beneficial in providing the user with multiple options to achieve an optimal balance of stiffness distribution, mass, weight distribution, inflection point location, and specific swing action, as will be described later.

[0104] While many previously disclosed embodiments focus on the metal tip portion 2000 and the nonmetallic root portion 1000, those skilled in the art will recognize that the previously disclosed and material properties of the nonmetallic root portion 1000 embodiments are equally applicable to embodiments of the nonmetallic tip portion 2000, and the previously disclosed and material properties of the metal tip portion 2000 embodiments are equally applicable to embodiments of the metal root portion 1000. In fact, the nonmetallic tip portion 2000 is preferred in some swing shafts (shafts used for golf clubs rather than putters). However, some kit embodiments may also include one or more metal tip portions 2000 and / or one or more metal root portions 1000.

[0105] In some embodiments, the root portion 1000 is formed of a nonmetallic root portion material having a root material density, a root portion mass of 35%-75% of the shaft mass, a root portion elastic modulus, and a root portion shear modulus, and having (i) a root portion area moment of inertia, (ii) a root portion polar moment of inertia, (iii) a root portion bending stiffness, and (iv) a root portion torsional stiffness at each point along the root portion length 1030. A simplified kit embodiment includes at least a first tip portion 2001 and a second tip portion 2002, which can be coupled to one or more root portions 1000 via a connector 3000. In one embodiment, the first tip portion 2001 is formed of a nonmetallic tip portion material having a first tip material density, a first tip portion elastic modulus, and a first tip portion shear modulus within 15% of the root material density, and having (i) a first tip portion area moment of inertia, (ii) a first tip portion polar moment of inertia, (iii) a first tip portion bending stiffness, and (iv) a first tip portion torsional stiffness at each point along the length of the first tip portion. Similarly, the second tip portion 2002 is formed of a nonmetallic tip portion material having a second tip material density within 15% of the root material density, a second tip portion elastic modulus, and a second tip portion shear modulus, and having (i) a second tip portion area moment of inertia, (ii) a second tip portion polar moment of inertia, (iii) a second tip portion bending stiffness, and (iv) a second tip portion torsional stiffness at each point along the length of the second tip portion. Those skilled in the art will understand that these fundamental properties also apply to embodiments that include a third tip portion 2003 or even a fourth tip portion 2004. While these embodiments disclose nonmetallic tip portions with densities similar to the root portion to be disclosed later, other embodiments incorporate tip portions 2000 with densities significantly greater than the root portion density, and some embodiments include metallic tip portions.

[0106] One embodiment includes at least two tip portions that meet one or more of the following criteria: (a) the bending stiffness of the largest second tip portion is at least 25% greater than that of the largest first tip portion, and (b) the torsional stiffness of the largest second tip portion is at least 35% greater than that of the largest first tip portion. For example, in Figure 18 In this embodiment, both the blue and white tip portions have a bending stiffness at least 25% greater than that of the green and red tip portions. Similarly, both the red and white tip portions have a torsional stiffness at least 50% greater than that of the green and blue tip portions. In another embodiment, at least two tip portions simultaneously meet criteria (a) and (b). Slow-swinging players using [the tool / equipment]... Figure 18The improved performance is most noticeable in the green and red tips (i.e., the tips with relatively low bending stiffness). Tips with torsional stiffness greater than bending stiffness (e.g., ...) Figure 18 The red tip (of the club) benefits players with average or above-average swing speeds, but due to their swing pattern, they may struggle to hit the ball high, for example, by failing to strike the ball on the backswing and often deviating significantly to the left in flight, partly due to the tip's lack of torsional stiffness. Conversely, golfers who have difficulty flipping the club and therefore tend to be positioned on the right side of the golf course will benefit from a tip with low torsional stiffness. Furthermore, golfers who strike the ball during the backswing will benefit most from a tip with characteristics similar to those found in the blue and white tips, namely, a tip with relatively high bending stiffness. Figure 18 An embodiment with torsional stiffness higher than bending stiffness, based on a low bending stiffness embodiment, is demonstrated. Figure 18 The red tip, while another embodiment can be implemented as a medium or high bending stiffness embodiment, such as a tip portion with EI=22.5 and GJ=25, or even a tip portion with EI=30 and GJ=35.

[0107] Figure 18 and Figure 20 The specific bending stiffness and torsional stiffness values ​​shown are associated with exemplary embodiments and help to discuss the relationship between the overall stiffness distribution of the multiple tip sections and the associated shaft. Figure 18 and Figure 20 The stiffness shown is in N*m 2 Unit. In one embodiment, the kit comprises at least two. Figure 18 or Figure 20 The tip portion has a stiffness of ±50% of the indicated value, while in another embodiment, the stiffness is ±35% of the indicated value, and in yet another embodiment, the stiffness is ±20% of the indicated value. Other embodiments of the kit have at least three... Figure 18 or Figure 20 The tip portion and the same positive and negative variation embodiments, or even other kits, have at least four Figure 18 Or the tip portion of 20 and the same positive and negative variations in the embodiment. In one embodiment, Figure 18 The bending stiffness and torsional stiffness shown are the maximum stiffness associated with a specific tip portion, while in an alternative embodiment they are the average stiffness associated with a specific tip portion, and in yet another alternative embodiment they are the minimum stiffness associated with a specific tip portion.

[0108] Figure 20The leftmost EI and GJ columns show the average bending stiffness and average torsional stiffness of the entire shaft, which consists of the same root section 1000 attached to four different tip sections 2000. The next two EI and GJ columns, labeled 0-33%, indicate the average bending stiffness and average torsional stiffness associated with the first third of the shaft length, starting from the near end 120. The two columns below that, labeled 33-66%, indicate the average bending stiffness and average torsional stiffness associated with the middle third of the shaft length. The next two columns, labeled 66-100%, indicate the average bending stiffness and average torsional stiffness associated with the first third of the shaft length, ending at the far end 110. The two columns below that, labeled 0-66%, indicate the average bending stiffness and average torsional stiffness associated with the two-thirds of the shaft length, starting from the near end 120. The two EI and GJ columns, labeled 33-100%, indicate the average bending stiffness and average torsional stiffness associated with the two-thirds of the shaft length ending at the far end (110). Finally, the last four columns, including two EI and two GJ columns, are labeled 0-66%, indicating the average bending stiffness and average torsional stiffness associated with the half-shaft length starting at the near end (120). The two EI and GJ columns, labeled 50-100%, indicate the average bending stiffness and average torsional stiffness associated with the half-shaft length ending at the far end (110).

[0109] Still referencing Figure 20 In one embodiment, the middle third and the third ending at the far end 110 of the shaft each have average bending stiffness and average torsional stiffness greater than or equal to the average overall shaft bending stiffness and average overall shaft torsional stiffness, respectively. The third beginning at the near end 120 of the shaft has average bending stiffness and average torsional stiffness less than 65% of the average overall shaft bending stiffness and average overall shaft torsional stiffness, respectively, in another embodiment less than 50%, and in yet another embodiment less than 35%. In fact, in other embodiments, for length columns of 33-66% and 66-100%, not only are the average bending stiffness and average torsional stiffness greater than or equal to the average overall shaft bending stiffness and average overall shaft torsional stiffness, respectively, they are also at least 15% greater than the average overall shaft bending stiffness and average overall shaft torsional stiffness, respectively, in another embodiment at least 20% greater, and in yet another embodiment 25% greater. However, another series of embodiments recognizes that negative performance returns are associated with large differences, and therefore introduces limitations: in one embodiment, the average overall shaft bending stiffness and average overall shaft torsional stiffness of the 33-66% and 66-100% length columns are no more than 50% greater than the average overall shaft bending stiffness and average overall shaft torsional stiffness, in another embodiment no more than 42.5%, and in yet another embodiment no more than 35%.

[0110] Adhering to the characteristic of a three-part shaft, in one embodiment, the third of the shaft terminating at the distal end 110 does not have the highest average bending stiffness, while in another embodiment, the third of the shaft terminating at the distal end 110 does not have the highest average torsional stiffness. Therefore, one kit embodiment includes two tip portions with different bending and torsional stiffnesses, such that (a) a first tip portion installed at the third of the shaft terminating at the distal end 110 does not have the highest average bending stiffness, and (b) a second tip portion installed at the third of the shaft terminating at the distal end 110 does not have the highest average bending stiffness.

[0111] Still referencing Figure 20 However, focus now is placed on the columns associated with the tip two-thirds length and the root two-thirds length. In one embodiment, the average bending stiffness of the 0-66% portion of the shaft is at least 55% of the average bending stiffness of the 33-100% portion of the shaft; in another embodiment, at least 60%; and in yet another embodiment, at least 65-80%. Focus now is placed on the average torsional stiffness. In one embodiment, the average torsional stiffness of the 0-66% portion of the shaft is at least 80% of the average torsional stiffness of the 33-100% portion of the shaft; in another embodiment, at least 85%; and in yet another embodiment, at least 85-110%.

[0112] Still referencing Figure 20 However, focus now is on the rightmost column associated with the tip half-length and the root half-length, where in one embodiment the average bending stiffness of the 0-50% portion of the shaft is at least 50% of the average bending stiffness of the 50-100% portion of the shaft, in another embodiment at least 60%, and in yet another embodiment at least 60-70%. Focus now is on the average torsional stiffness, where in one embodiment the average torsional stiffness of the 0-50% portion of the shaft is at least 90% of the average torsional stiffness of the 50-100% portion of the shaft, in another embodiment at least 95%, and in yet another embodiment at least 95-115%.

[0113] largely re-referenced Figure 18 In one embodiment, the average bending stiffness of the first tip portion is 10-50 N*m. 2 The average bending stiffness of the second tip is 10-50 N*m. 2 In another embodiment, the average torsional stiffness of the first tip portion is 5-40 N*m. 2 The average torsional stiffness of the second tip is 5-40 N*m. 2 In other embodiments, the bending stiffness of the tip portion is reduced to include 10-40 N*m. 2 Within this range, in another embodiment, it includes 12.5-37.5 N*m.2 Within this range. In other embodiments, the torsional stiffness of the tip portion is reduced to include 5-35 N*m. 2 Within this range, in another embodiment, it includes 7.5-30 N*m. 2 .

[0114] In one specific embodiment, the kit includes at least two pointed segments, wherein the bending stiffness of the pointed portions differs by at least 5 N*m. 2 In another embodiment, the difference is at least 10 N*m 2 In another embodiment, the difference is at least 15 N*m. 2 In other embodiments, the difference in flexural stiffness does not exceed 30 N*m. 2 In another embodiment, it does not exceed 25 N*m 2 In yet another embodiment, it does not exceed 20 N*m 2 In another embodiment, the kit includes at least two pointed segments, wherein the torsional stiffness of the pointed portions differs by at least 5 N*m. 2 In another embodiment, at least 10 N*m 2 In another embodiment, the torsional stiffness difference is at least 15 N*m². In an additional embodiment, the torsional stiffness difference does not exceed 35 N*m. 2 In another embodiment, it does not exceed 30 N*m 2 In yet another embodiment, it does not exceed 25 N*m 2 .

[0115] The kit may also include at least three or even at least four tip segments, and the stiffness relationship just disclosed can be applied to any pair of tip segments or even all of the tip segments. In these embodiments, at least half of the tip segments have different average bending stiffness and different average torsional stiffness, for Figure 18 The same applies to one embodiment, while in another embodiment, each tip segment may have unique and different bending and / or torsional stiffness from the other tip segments. In yet another such embodiment, none of the tip segments have an average bending stiffness exceeding three times the average bending stiffness of the other tip segments, and none of the tip segments have an average torsional stiffness exceeding five times the average torsional stiffness of the other tip segments.

[0116] Furthermore, the relationship between the stiffness of the tip and the stiffness of the root portion is crucial for producing products that do not give the impression of the user swinging a rigid board or a board with pointed, noodle-like tips. Therefore, in one embodiment, the average bending stiffness of the root portion is at least 40 N*m. 2 The average torsional stiffness at the root is at least 20 N*m. 2 In another embodiment, the average root bending stiffness is at least 50 N*m. 2The average torsional stiffness at the root is at least 25 N*m. 2 In another embodiment, the average root bending stiffness is 50-110 N*m. 2 The average torsional stiffness at the root is 20-70 N*m. 2 In another embodiment, the average root bending stiffness is 60-100 N*m. 2 The average torsional stiffness at the root is 25-60 N*m. 2 When the average root portion bending stiffness is at least three times that of one of the selected tip portions and at least twice that of the second selected tip portion, a significant difference in preferred fit flexibility, feel, and performance is observed. In another embodiment, the average root portion bending stiffness is 3-6 times that of one of the tip portions and 2-4 times that of the second selected tip portions. In these embodiments, the stiffness of the root portion provides lower shot dispersion and consistency for low-speed swing golfers, while the stiffness of the tip portion helps low-speed swing golfers achieve a preferred launch angle.

[0117] Adhering to the disclosure of the root portion 1000, in one embodiment, the average bending stiffness of the root portion is at least twice the average torsional stiffness of the root portion. In another embodiment, the average bending stiffness of the root portion does not exceed four times the average torsional stiffness of the root portion. In another embodiment, the average bending stiffness of the root portion is greater than the bending stiffness of at least 50% of the tip portions in the kit; in yet another embodiment, the average bending stiffness of the root portion is greater than the bending stiffness of all the tip portions in the kit.

[0118] In another embodiment, at least one of the attenuating tips in a kit having at least two tip portions has an average tip portion bending stiffness within 70% of the average root portion bending stiffness, and at least one tip portion has an average tip portion bending stiffness at least 70% less than the average root portion bending stiffness. Another embodiment includes at least three tip portions in a kit, wherein at least two have an average tip portion bending stiffness within 70% of the average root portion bending stiffness. Yet another embodiment includes at least four tip portions in a kit, wherein at least two have an average tip portion bending stiffness within 70% of the average root portion bending stiffness, and at least two have an average tip portion bending stiffness at least 70% less than the average root portion bending stiffness.

[0119] Similarly, in another embodiment, at least one of the attenuating tips in a kit having at least two tip portions has an average tip portion torsional stiffness within 30% of the average root portion torsional stiffness, and at least one tip portion has an average tip portion torsional stiffness at least 60% less than the average root portion torsional stiffness. Another embodiment includes at least three tip portions in a kit, wherein at least two have an average tip portion torsional stiffness within 30% of the average root portion torsional stiffness; yet another embodiment includes at least four tip portions in a kit, wherein at least two have an average tip portion torsional stiffness within 30% of the average root portion torsional stiffness, and at least two have an average tip portion torsional stiffness at least 60% less than the average root portion torsional stiffness.

[0120] In another embodiment, at least one of the attenuating tips in a kit having at least two tip portions has an average tip portion bending stiffness of 50%-60% of the average root portion bending stiffness, and at least one tip portion in the kit has an average tip portion torsional stiffness of 75%-90% of the average root portion torsional stiffness. Another embodiment includes at least three tip portions in a kit, wherein at least two have an average tip portion bending stiffness of 50%-60% of the average root portion bending stiffness. Yet another embodiment includes at least four tip portions in a kit, wherein at least two have an average tip portion bending stiffness of 50%-60% of the average root portion bending stiffness, and at least two have an average tip portion torsional stiffness of 75%-90% of the average root portion torsional stiffness.

[0121] Similarly, in another embodiment, at least one tip portion of a kit having at least two tip portions has an average tip portion torsional stiffness of 75%-90% of the average root portion torsional stiffness, and at least one tip portion of the kit has an average tip portion torsional stiffness of 20%-35% of the average root portion torsional stiffness. Another embodiment includes at least three tip portions in a kit, wherein at least two have an average tip portion torsional stiffness of 75%-90% of the average root portion torsional stiffness. Yet another embodiment includes at least four tip portions in a kit, wherein at least two have an average tip portion torsional stiffness of 75%-90% of the average root portion torsional stiffness, and at least two have an average tip portion torsional stiffness of 20%-35% of the average root portion torsional stiffness. This invention often relates to the characteristic of "at least one tip portion in a kit," but this disclosure is not limited to "kit" embodiments, but also includes individual shafts, whether integral or separate (permanently joined or releasably joined) to possess the disclosed properties and relationships.

[0122] In one preferred embodiment, the second tip portion is no more than 50% heavier than the first tip portion; in another embodiment, no more than 30% heavier; in yet another embodiment, no more than 20% heavier; in still another embodiment, no more than 10% heavier; and in yet another embodiment, no more than 5% heavier. Further, the first tip portion is 25%-99% of the root portion's mass, and the second tip portion is 25%-99% of the root portion's mass; in another embodiment, the tip portion is 30%-70% of the root portion's mass; and in yet another embodiment, the tip portion is 35%-60% of the root portion's mass. In one embodiment, the tip portion's mass is no more than 40 grams; in other embodiments, it is no more than 35 grams, 30 grams, 25 grams, or 20 grams. In another embodiment, the root portion's mass is no more than 70 grams; in another embodiment, no more than 60 grams; and in yet another embodiment, no more than 45 grams. In embodiments involving hybrid irons and irons, the mass of individual components may be slightly heavier. For example, in one embodiment, the mass of the tip portion does not exceed 50 grams, while in other embodiments it does not exceed 40 grams, 35 grams, 30 grams, or 25 grams; in another embodiment, the mass of the root portion does not exceed 90 grams, and in other embodiments it does not exceed 80 grams, 70 grams, or 60 grams. In other embodiments, the relationship between the mass of the second tip portion and the mass of the first tip portion disclosed in this paragraph can also be applied to the mass of the third and fourth tip portions relative to the mass of the first tip portion, as well as relative to the mass of the tip portion and the mass of the root portion, and the total mass.

[0123] In some kit embodiments, there are at least two tip portions, with a mass variation of at least 15% in one embodiment, at least 25% in another, and at least 40% in yet another, thus presenting a wider range of options to ensure that the user can tangibly perceive the differences between the various choices. Similarly, in some kit embodiments, there are at least two root portions, with a mass variation of at least 15% in one embodiment, at least 25% in another, and at least 40% in yet another, thus presenting a wider range of options. Likewise, in some kit embodiments, there is at least a connector portion, with a mass variation of at least 15% in one embodiment, at least 25% in another, and at least 40% in yet another, thus presenting a wider range of options.

[0124] One specific kit embodiment includes at least three tip portions (referred to as a tip family) and / or at least three root portions (referred to as a root family), wherein at least two of these components in the same family have a mass within 5% of the mass of the other components (measured relative to the lightest family component), while the other components in the family have a mass at least 15% heavier than the lightest family component. In another kit embodiment, at least two of these components in the same family have a mass within 2.5% of the mass of the other components (measured relative to the lightest family component), while the other components in the family have a mass at least 25% greater than the lightest family component. Another kit embodiment includes at least two tip portions and / or at least two root portions, wherein at least one component in the same family has a mass at least 15% heavier than the lightest family component, while in another embodiment, at least one component in the same family has a mass at least 15%-45% heavier than the lightest family component, and in even more specific embodiments, at least 15%-30% heavier.

[0125] The flexural and torsional stiffness of the tip and root portions can vary considerably, while maintaining nearly identical quality (if desired) by incorporating fibers with different tensile strengths and / or modifying the fiber layup orientation or density. In one embodiment, the number of unidirectional prepreg layers in the root portion differs from that in the tip portion. In another embodiment, the fiber orientation angle between adjacent unidirectional layers in the root portion is different from that between adjacent unidirectional layers in the tip portion. In yet another embodiment, the resin content in the root portion differs from that in the tip portion, and in yet another embodiment, the resin content in the root portion is greater than that in the tip portion. The term "resin content" refers to the weight ratio of resin to the total weight of the fiber-reinforcing resin. The weight of the resin is obtained by chemically decomposing or removing only the resin from the fiber-reinforcing resin being tested, and then subtracting the total weight of the fibers from the previously measured weight of the fiber-reinforcing resin. To chemically remove resin from the fiber-reinforcing resin, a heated nitric acid solution, for example, is used. Further, to chemically remove resin from, for example, prepreg materials, methyl ethyl ketone, for example, is used.

[0126] In one embodiment, a preferred balance and performance was found when the tip mass was 20-30 grams, the root mass was 40-50 grams, and the connector mass was 5-17.5 grams. Indeed, the connector mass preferably does not exceed 50% of the tip mass and the root mass, while in another embodiment, the connector mass does not exceed 75% of the tip mass and 35% of the root mass, and in yet another embodiment, the connector mass is 35%-60% of the tip mass and 20%-35% of the root mass. Another embodiment further recognizes that simply minimizing the connector mass is not the goal; in this embodiment, the connector mass is at least 25% of (a) the first tip mass and (b) the second tip mass. Similarly, in another embodiment, the first tip mass is 35%-85% of the root mass, the second tip mass is 35%-85% of the root mass, and in yet another embodiment, these ranges are narrowed to 40%-80%, 45%-75%, and 50%-70%.

[0127] Now referencing the stiffness relationship and Figure 18 In another embodiment, the bending stiffness of the largest second tip portion is at least 50% greater than the bending stiffness of the largest first tip portion, and the torsional stiffness of the largest second tip portion is at least 75% greater than the torsional stiffness of the largest first tip portion. In another embodiment, the bending stiffness of the largest second tip portion is 35%-150% greater than the bending stiffness of the largest first tip portion, and the torsional stiffness of the largest second tip portion is 75%-350% greater than the torsional stiffness of the largest first tip portion. The kit of another embodiment includes a first tip portion whose torsional stiffness is greater than the bending stiffness of the largest first tip portion, for example... Figure 18 The red tip, and the second tip portion whose torsional stiffness is less than its bending stiffness, for example... Figure 18 The tip may be green, blue, or white. In another such embodiment, the torsional stiffness of the largest first tip portion is at least 30% greater than the bending stiffness of the largest first tip portion, and the torsional stiffness of the largest second tip portion is at least 50% less than the bending stiffness of the largest first tip portion.

[0128] Compared to the tip portion 2000 and Figure 18Similarly, in embodiments with multiple root portions 1000, the bending stiffness and torsional stiffness can also be varied, thereby providing the advantages and properties described in relation to variations in the tip portion 2000. For example, in one embodiment, the bending stiffness of the largest second root portion is at least 25% greater than that of the largest first root portion, and the torsional stiffness of the largest second root portion is at least 50% greater than that of the largest first root portion. In yet another embodiment, the bending stiffness of the largest second root portion is 25%-150% greater than that of the largest first root portion, and the torsional stiffness of the largest second root portion is 50%-350% greater than that of the largest first root portion. Another embodiment's kit includes a first root portion with a maximum torsional stiffness greater than that of the largest first root portion and a second tip portion with a maximum torsional stiffness less than that of the largest second root portion. In another such embodiment, the torsional stiffness of the largest first portion is at least 30% greater than the bending stiffness of the largest first portion, and the torsional stiffness of the largest second portion is at least 50% less than the bending stiffness of the largest first portion.

[0129] The relationship between length and center of gravity also plays a crucial role in providing an adjustable shaft. The adjustable shaft offers a unique relationship that enhances fit, performance, and feel, while also distributing stress within the shaft and preventing stress build-up that negatively impacts durability. Each tip section (2001, 2002, 2003, 2004) has a tip length of 2030, each root section (1000, 1001, 1002, 1003, 1004) has a root length of 1030, and each connector (3000, 3001, 3002, 3003, 3004) has a length from... Figure 21The connector length 3030 is measured end-to-end. In an embodiment having a single root portion 1000, at least one connector 3000, and at least two tip portions 1000, the length of the first tip portion is at least 25% smaller than the root portion length 1030, the length of the second tip portion is at least 25% smaller than the root portion length 1030, and the connector length 3030 does not exceed 50% of the length of any tip portion. In another embodiment, the length of each tip portion is at least 25% of the root portion length 1030, and the connector length 3030 is at least 10% of the length of any tip portion. In yet another embodiment, the length of the first tip portion is 25%-80% shorter than the root portion length 1030, the length of the second tip portion is 25%-80% shorter than the root portion length 1030, and in yet another embodiment, at least two tip portions 2000 have the same length, and at least one tip portion 2000 has a different length. For swinging the club, the tip length is preferably 8-26", the root length is preferably 22-40", and the connector length is preferably 0.5-8.0". In another embodiment, the tip length is 10-22", the root length is 26-36", and the connector length is 1.0-4.0". In one embodiment, each tip length is at least 20% of the shaft length 130", while in another embodiment, each tip length does not exceed 40% of the shaft length 130, and in yet another embodiment, it does not exceed 25%-37.5%.

[0130] In another embodiment, regardless of which tip portion is installed, the distance from the shaft center of gravity of shaft 100 to the shaft CG of the proximal shaft end 120 does not exceed 65% of the shaft length 130, in yet another embodiment it does not exceed 60%, and in still another embodiment it does not exceed 55%. In yet another embodiment, the shaft CG distance is greater than the distance from the proximal shaft end 120 to any part of the connector 3000, thus the shaft center of gravity is located between the connector 3000 and the distal shaft end 110. A family of embodiments achieves any of the relationships disclosed herein while controlling the shaft CG distance, allowing for a shaft CG distance change of 5 mm or less, while simultaneously achieving associated relationships, whether or not these relationships are related to and associated with the stiffness of different tip portions, root portions, and / or connectors or other aspects. Further, this may apply only to two portions in a particular kit, up to applying to every portion in the kit. Another embodiment of this family achieves a shaft CG distance change of 3 mm or less, and in another embodiment, a change of 2 mm or less. Changing the CG distance of the control shaft requires a unique configuration of the weight distribution of one or more components, which are interchangeable to achieve the target relationship and thus change the CG distance of the control shaft.

[0131] The variation in stiffness along the 130mm length of the shaft significantly impacts the hitability and feel of the specific combination of the heel (1000mm), tip (2000mm), and connector (3000mm). Furthermore, selectively designing abrupt stiffness changes along a relatively short length within a specific region can provide an ideal transition point. This contrasts with traditional shaft designs, which strive for a smooth stiffness transition throughout the entire length and describe abrupt stiffness changes as undesirable. Moreover, for some swing types, abrupt stiffness changes along a relatively short length within a specific region result in more efficient energy transfer.

[0132] In one such embodiment, as shown in Figures 19(A) to (D) and 23(A) to (D), the bending stiffness of the shaft exceeds 125 N*m over a distance not exceeding 15% of the shaft length 130. 2 The torsional stiffness of the shaft exceeds 100 N*m at a distance no longer than 15% of the shaft length of 130 mm. 2 In another embodiment, the bending stiffness of the shaft exceeds 150 N*m over a distance no longer than 15% of the shaft length 130. 2 The torsional stiffness of the shaft exceeds 115 N*m over a distance no longer than 15% of the shaft length of 130 mm. 2 .

[0133] Other embodiments recognize the minimum distance at which the aforementioned stiffness abrupt change occurs. For example, in these embodiments, the disclosed stiffness level is not limited to occurring at a distance not exceeding 15% of the shaft length 130, but in these embodiments it must also occur at a distance of at least 3.5% of the shaft length 130, and in other embodiments at least 5%. The shaft 100 may also include a reinforced region located between a first point 5" from the proximal end (120) of the shaft and a second point 36" from the proximal end (120) of the shaft, wherein the shaft bending stiffness at a location within the reinforced region is (A) at least 100% greater than the minimum first tip bending stiffness and the minimum second tip bending stiffness, and (B) at least 50% greater than the minimum root bending stiffness. In another embodiment, the shaft bending stiffness at a location within the reinforced region is (A) at least 125 N*m. 2 (B) is at least 200% greater than both the minimum first tip portion bending stiffness and the minimum second tip portion bending stiffness, and (C) is at least 75% greater than the minimum root portion bending stiffness.

[0134] However, another embodiment recognizes the diminishing returns and negative properties associated with excessive stiffness growth, and therefore limits growth so that the bending stiffness of the shaft does not exceed 600 N*m. 2 The torsional stiffness of the pole body shall not exceed 450 N*m. 2 ,For example Figure 25The illustrated embodiment includes a joint comprising a steel alloy component. In yet another embodiment, the bending stiffness of the rod does not exceed 300 N*m. 2 The torsional stiffness of the pole body shall not exceed 250 N*m. 2 ,For example Figure 24 The illustrated embodiment includes a titanium alloy component as the joint. Further, in yet another embodiment, the bending stiffness of the rod does not exceed 250 N*m. 2 The torsional stiffness of the pole body shall not exceed 200 N*m. 2 For example, the embodiment shown in Figure 23(A) includes an aluminum alloy component. Those skilled in the art will understand that these stiffnesses are attributable not only to material properties but also to the unique range targeted and the joint 3000 specifically designed to achieve these ranges, while balancing trade-offs associated with weight and durability issues common to stress abrupt changes over shorter lengths.

[0135] Figure 21 and 22 The interchangeable connector embodiment incorporates a tip connector portion 3300, a root connector portion 3400, and a fastener 3500. The tip connector portion 3300 engages with the tip portion 2000 along a tip engagement length 3310. In the illustrated embodiment, the tip portion 2000 extends into the tip connector portion 3300, although the reverse is also possible. The tip engagement length 3310 does not need to be a continuous contact between the tip portion 2000 and the tip connector portion 3300; a mating length is sufficient, as most embodiments will incorporate grooves or channels on one or more surfaces to improve adhesive strength when the tip connector portion 3300 is bonded to the tip portion 2000. Furthermore, the "matting length" does not require direct contact between the tip portion 2000 and the tip connector portion 3300, as they can be separated from each other by a single layer of adhesive.

[0136] Similarly, the root connector portion 3400 is coupled to the root portion 1000 along the root bonding length 3410. In the illustrated embodiment, the root portion 3400 extends into the root connector portion 1000, although the reverse is also possible. The tip bonding length 3310 and the root bonding length 3410 significantly affect the previously disclosed stiffness abrupt changes over relatively short lengths in specific regions, and the associated desirable properties. The tip bonding length 3310 is at least as long as the outer diameter of the tip portion 2070, and in another embodiment, it is twice the outer diameter of the tip portion 2070. Likewise, the root bonding length 3410 is at least as long as the outer diameter of the tip portion 2070, and in another embodiment, it is twice the outer diameter of the tip portion 2070. Increasing the tip bonding length 3310 and / or the root bonding length 3410 provides advantages associated with a larger bonding area, load distribution, and lower stress, increases in these lengths that can be detrimental to the performance of the shaft 100 because the stiffness abrupt changes extend over an excessive portion of the shaft length 130. Therefore, in one embodiment, the tip engagement length 3310 and the root engagement length 3410 do not exceed 10 times the outer diameter of the tip portion 2070, while in another embodiment they do not exceed 7 times the outer diameter of the tip portion 2070, and in yet another embodiment they do not exceed 5 times the outer diameter of the tip portion 2070. In another embodiment, the tip engagement length 3310 and the root engagement length 3410 are at least 0.500", in another embodiment at least 0.625", and in yet another embodiment at least 0.750".

[0137] exist Figure 21 and 22 In one embodiment, fastener 2500 is configured to engage with both tip connector portion 3300 and root connector portion 3400. In this embodiment, fastener 3500 is an internally threaded sleeve that engages with external threads on root connector portion 3400, securing tip connector portion 3300 within root connector portion 3400; however, in another embodiment, the configuration may be reversed. Fastener 3500 does not need to be threaded into one of tip connector portion 3300 and root connector portion 3400; other mechanical engagement methods can be applied. Further, in some embodiments, fastener 3500 does not need to engage with both tip connector portion 3300 and root connector portion 3400 simultaneously. For example, in an embodiment with metal tip portion 2000, fastener 3500 may engage directly with tip portion 2000. Root connector portion 3400 may be external to and within root portion 1000, receiving a portion of root portion 1000. Fastener 3500 provides another adjustable point in the system. In one embodiment, the kit includes at least two fasteners 3500, one of which has a density at least twice that of the other.

[0138] In one embodiment, at least a portion of the connector 3000 is made of a metallic material, while in another embodiment, the tip connector portion 3300 and the root connector portion 3400 are formed of a metallic material, and in yet another embodiment, the tip connector portion 3300, the root connector portion 3400, and the fastener 3500 are formed of a metallic material. In yet another embodiment, the connector density of any of the just disclosed metallic components does not exceed three times the density of the root portion. The connector 3000 may also include a compressible adapter 3600 located at a location susceptible to durability issues, such as the interface between the exposed end of the root portion 1000 and the fastener 3500, as... Figure 22 As shown, this area experiences significant shaft deflection 100 during a golf swing, and contact between the exposed section of the root portion 1000 and the metal fastener 3500 can potentially damage the root portion 1000, especially when the root portion is made of a non-metallic material. Therefore, in one embodiment, the tip connector portion 3300 and the root connector portion 3400 are designed to ensure a gap of at least 0.5 mm between the fully engaged fastener 3500 and one end of the root portion 1000; in another embodiment, this gap is at least 1.0 mm; and in yet another embodiment, this gap does not exceed 5.0 mm.

[0139] like Figure 22 As shown, the length of the fastener 3500, measured along the shaft axis from one end to the other, is less than the tip engagement length 3310, less than the root engagement length 3410 in another embodiment, and less than half the length of at least one of the tip engagement length 3310 and the root engagement length 3410 in yet another embodiment. The fastener 3500 can be designed to engage with a fastening tool, thereby fully securing the component. In a further embodiment, the tool can be a torque-limiting tool to prevent the user from overtightening either component and damaging it. In another embodiment, the fastener 3500 is designed so that it cannot be fully engaged with at least one of the other parts of the connector 3000 without the use of a tool; in other words, this work cannot be done by hand. One or more tool engagement features 3520, including protrusions or recesses, can be formed on the outer surface of the fastener 3500 to engage with complementary structures on the fastening tool, such as... Figure 22 As shown.

[0140] Furthermore, the fastener 3500 may incorporate a fastener tapered portion 3510, which may be integrated with the fastener 3500, or may be as follows: Figure 22The fastener tapered portion 3510 is shown as a separate component. It has a taper angle measured from the outer surface to the inner surface, ranging from 10 to 60 degrees, 15 to 50 degrees in another embodiment, and 20 to 45 degrees in yet another embodiment. The fastener tapered portion 3510 provides a smoother transition from the root to the tip and can be used to conceal changes in outer diameter and further disperse stress. The volume of the fastener tapered portion 3510 is at least 50% of the volume of the fastener 3500, but its mass does not exceed 25% of the mass of the fastener 3500. Additionally, the fastener 3500 may include an undercut 3530 to further disperse stress and prevent stress escalation associated with sharp metal edges. The undercut 3530 forms an angle of at least 15 degrees with the horizontal plane, extending over at least 25% of the thickness of the fastener 3500. Another advantage of the fastener tapered portion 3510 embodiments is that the undercut 3530 is concealed, and in some embodiments extends into the undercut 3530. This area experiences significant bending at the tip and slight bending of the fastener 3500, therefore avoiding sudden interface changes is preferred. The tapered portion 3510 of the fastener may be formed of a non-metallic material and also serves to dampen vibrations transmitted across the fastener 3500. In one embodiment, the tapered portion 3510 of the fastener is formed of a highly elastic material with a mass of less than 10 grams.

[0141] The mass distribution and the disclosed stiffness relationship can be achieved through various methods. In one method, the tip portion 2000 may be hollow, or at least partially hollow, with its tip portion sidewall thickness 2050 varying between a minimum and a maximum tip portion sidewall thickness. In one such embodiment, the maximum tip portion sidewall thickness is at least 25% greater than the minimum tip portion sidewall thickness. In another embodiment, the maximum tip portion sidewall thickness is 25%–75% greater than the minimum tip portion sidewall thickness. Further, in one embodiment, the sidewall thickness of the tip connector portion 3300 coupled with the tip portion 2000 is less than the maximum tip portion sidewall thickness; in another embodiment, the sidewall thickness of the root connector portion 3400 coupled with the root portion 1000 is less than the maximum root portion sidewall thickness. Further still, in yet another embodiment, the maximum tip portion sidewall thickness is greater than the root portion sidewall thickness 4050 of a portion of the root portion 4000.

[0142] The root portion 1000 may have a constant outer diameter 1070, or the outer diameter may gradually decrease, with or without steps; similarly, the tip portion 2000 may have a constant outer diameter 2070, or the inner diameter may gradually decrease, with or without steps. In one embodiment, at least one of the root portion 1000 and the tip portion 2000 includes a portion with a constant outer diameter, while in another embodiment, both the root portion 1000 and the tip portion 2000 include portions with constant outer diameters. In one embodiment, the entire root portion 1000 has a constant outer diameter, while in another embodiment, the tip portion 2000 simultaneously has a tapered tip section 2080 and a constant diameter tip section 2090, such as... Figure 17 As shown, there are two tip portion constant diameter segments 2090 separated by a tip portion tapered segment 2080. In one embodiment, the length of the tip portion tapered segment 2080 is preferably greater than the length of the tip portion constant diameter segment 2090 or the length of each segment, while in another embodiment, the length of the tip portion tapered segment 2080 is 50%-80% of the length of the tip portion 2030. Regardless of whether the tapering is in the root portion 1000, the tip portion 2000, or both, in a further embodiment, the tapering causes the outer diameter to vary by at least 5% from the minimum outer diameter.

[0143] Positioning a significant change in outer diameter at a point of stiffness reinforcement can significantly affect the inflection point of the shaft 100. In one such embodiment, the shaft outer diameter decreases by at least 15% at the connector 3000 from the root portion 1000 to the tip portion 2000, by at least 20% in another embodiment, and by at least 25% in yet another embodiment. However, an overly significant change in shaft outer diameter at the connector 3000 can negatively impact the performance, durability, and aesthetics of the shaft 100. Therefore, in one embodiment, the shaft outer diameter decreases by no more than 45% at the connector 3000 from the root portion 1000 to the tip portion 2000, by no more than 40% in another embodiment, and by no more than 35% in yet another embodiment. The outer diameter of the fastener 3500 can gradually decrease, which helps to visually conceal the significant change in the outer diameter of the shaft 100.

[0144] As previously described, selectively designing stiffness abrupt changes over a relatively short length within a specific region can yield an ideal turning point. Therefore, adjusting the location of the stiffness abrupt changes along the length of the root portion 1000 and the tip portion 2000 allows for high flexibility in turning point positioning. One such embodiment maintains a high degree of consistency in the turning point location while providing the golfer with two distinct tip portions 2000 that differ significantly in both bending and torsional stiffness. In this embodiment, the shaft has a first turning point distance when including the first tip portion and a second turning point distance when including the second tip portion. Regardless of variations in the characteristics disclosed herein between the first and second tip portions, the second turning point distance is within 5% of the first turning point distance; in another embodiment, it is within 3%; and in yet another embodiment, it is within 1%. The turning point distance is the distance along the initial shaft axis from the proximal end 120 of the shaft to the point of maximum deflection. In the aforementioned embodiments, the turning point distance does not vary significantly, while in one embodiment, the maximum turning point deflection relative to the initial shaft axis associated with the turning point distance is significantly different for the first tip portion compared to the second tip portion. In fact, in one embodiment, the maximum turning point deflection associated with a shaft having one tip portion is at least 10% greater than another maximum turning point deflection associated with a shaft having a different tip portion, at least 15% in another embodiment, at least 20% in yet another embodiment, however, not more than 100% in another series of embodiments, and not more than 90% and 80% in other additional embodiments.

[0145] Previous embodiments incorporated tip portions of equal length, with abrupt stiffness changes aiding in control of inflection point positioning while accommodating variations in tip portion length up to 20%. However, in these embodiments, the first and second inflection point distances were measured from the distal shaft 110, not the proximal shaft 120. In a further embodiment, the inflection point is located within 6" of the connector edge. By providing at least two tip portions with different tip portion lengths, various kit embodiments allow users to analyze the impact of inflection point positioning. The two tip portions include a longer tip portion that is at least 15% longer than the shorter tip portion, at least 25% longer in another embodiment, and at least 35% longer in yet another embodiment. The two tip portions of different lengths can have the same flexural stiffness distribution and / or torsional stiffness distribution. In another embodiment, the longer tip portion is no more than 75% longer than the shorter tip portion, no more than 65% longer in yet another embodiment, and no more than 50% longer in yet another embodiment.

[0146] refer to Figures 19(A) to 19(D)One embodiment has at least one of the following: (a) a minimum first tip portion bending stiffness, and (b) a minimum second tip portion bending stiffness, which is at least 30% smaller than the root portion bending stiffness of a portion of the root portion, and the maximum root portion bending stiffness does not exceed 70% of the maximum shaft bending stiffness. In a further embodiment, at least one of the following: (a) the minimum first tip portion bending stiffness and (b) the minimum second tip portion bending stiffness are at least 50% smaller than the root portion bending stiffness of a portion of the root portion, the maximum root portion bending stiffness does not exceed 55% of the maximum shaft bending stiffness, and at least one of the following: (a) the maximum first tip portion bending stiffness and (b) the maximum second tip portion bending stiffness are at least 30% of the maximum root portion bending stiffness.

[0147] Similarly, another embodiment has at least one of the following: (a) a minimum first tip torsional stiffness, and (b) a minimum second tip torsional stiffness, which is at least 30% smaller than the root torsional stiffness of a portion of the root portion, and the maximum root torsional stiffness does not exceed 70% of the maximum shaft torsional stiffness. In a further embodiment, at least one of the following is true: (a) the minimum first tip torsional stiffness and (b) the minimum second tip torsional stiffness are at least 50% smaller than the root torsional stiffness of a portion of the root portion, the maximum root torsional stiffness does not exceed 55% of the maximum shaft torsional stiffness, and at least one of the following is true: (a) the maximum first tip torsional stiffness and (b) the maximum second tip torsional stiffness are at least 60% of the maximum root torsional stiffness. Additionally, in one specific embodiment, the shaft bending stiffness is constant for at least 10% of the shaft length, and the shaft torsional stiffness is constant for at least 10% of the shaft length.

[0148] like Figures 23(A) to 23(D) As shown in the embodiments, the bending stiffness and torsional stiffness vary over most of the shaft between the proximal end 120 and the point of maximum stiffness, while remaining constant over most of the shaft between the point of maximum stiffness and the distal end 110. In a further embodiment, the bending stiffness and torsional stiffness vary by less than 70% over a portion of the shaft between the proximal end 120 and the point of maximum stiffness, less than 60% in another embodiment, and less than 50% in yet another embodiment. However, the bending stiffness varies by at least 5% over a portion of the shaft between the proximal end 120 and the point of maximum stiffness.

[0149] Any of the above disclosures can be incorporated into embodiments of methods for adapting golfer shafts to golf club shafts, as well as methods for selling golf club shafts and methods for constructing or assembling golf club shafts. In one embodiment, the reference to “kit” as used throughout the disclosure includes a system of components sold as a single sales unit, such as when packaged together in a single box; however, “kit” also includes situations where these components can be tried and / or purchased together, although these components may ultimately be purchased separately, or even from different locations or sources.

[0150] For example, this could be a retail display containing multiple tip sections and / or multiple root sections, from which users or fitness enthusiasts can mix and match parts for experimentation and / or purchase parts individually to build a single shaft, even remotely ordering and assembling. For instance, a golf retailer could have a wide variety of parts, including at least several different tip sections, which potential users or fitness enthusiasts can combine and assemble into a golf shaft, preferably with some form of adaptation assistance (whether from a professional, instruction manual, app, or other software system). The potential user can then attach the assembled shaft to the clubhead to create a golf club, and then take the club to the hitting area to evaluate the combination by hitting multiple golf balls. Potential users can repeat this process multiple times with different part combinations until they obtain the combination that best suits their swing and ideal ball flight characteristics. The software system can guide potential users by recommending component combinations based on data received from flight monitors or other ball flight recording or simulation devices. For example, based on different bending and / or torsional stiffness characteristics, the system can analyze the collected data and identify and selectively recommend different tip sections. These characteristics help users generate test data that is more likely to resemble the flight characteristics of the target ball selected by the user. Potential users then purchase only the components necessary to assemble their ideal combination and order a shaft composed of preferred components that can be assembled remotely and mailed to the user. Therefore, in this embodiment, the kit purchased by the user does not contain multiple versions of at least one component required to build a golf club; however, at least one essential component has multiple versions available for potential users to choose from and / or experiment with and / or purchase or order. Thus, in one embodiment, the kit may be a retail display or even a self-service option. Furthermore, the online ordering system still functions as the disclosed kit, allowing users to select from multiple versions of at least one essential component and purchase other components necessary to create the final shaft, whether purchased all at once or individually in installments.

[0151] One embodiment includes the following steps: (a) selecting a first tip portion from a plurality of different tip portions; (b) assembling a first shaft including the selected first tip portion; (c) attaching a clubhead to the first shaft to create a first golf club; (d) hitting a plurality of golf balls with the first golf club to collect multiple ball flight data associated with the first golf club; (e) selecting a second tip portion from a plurality of different tip portions based on at least one of the multiple ball flight data; (f) removing the clubhead and the first tip portion from the first shaft and installing the second tip portion to create a second shaft; (g) attaching the clubhead to the second shaft to create a second golf club; and (h) hitting a plurality of golf balls with the second golf club to collect multiple ball flight data associated with the second golf club. The software system can analyze the first ball flight data and the second ball flight data, and provide a visual comparison between the results of preparing the two golf clubs. Furthermore, the system can recommend a suggested tip portion between the two, or suggest trying a third tip portion and repeating the process. The method may also include the step of selecting a preferred combination of components based on a comparison of ball flight data associated with a first golf club and ball flight data associated with a second golf club, and may also include the step of deciding to purchase.

[0152] Any or all of these steps can occur in a virtual or simulated environment. For example, a potential user can upload a video of their swing, or data representing their swing, to a computer system. The software system can evaluate the swing, including attributes such as swing speed and acceleration distribution and angle of attack, and suggest the optimal combination of components to produce a tailored, preferred golf shaft that achieves optimal performance based on the evaluated golf swing. In a further embodiment, the system can simulate multiple shafts, determine simulated performance characteristics for each shaft, and display these simulated performance characteristics to the potential user so that the potential user can see how the combination affects the simulated ball flight. The software system may also include a step of evaluating ball flight data, which includes any or all of the data collected by commercially available systems such as SkyGolf SkyTrak, Rapsodo, FlightScope Mevo, Voice Caddie SC300, and equivalents.

[0153] Additionally, the disclosed interchangeable tip portion embodiments and methods can be used in the creation of a one-piece composite golf club shaft having a flexural and torsional stiffness distribution that best matches a particular user's golf swing. In other words, in one embodiment, the interchangeable tip portion shaft system is used in an adaptation process to experimentally identify preferred flexural and torsional stiffness distributions, which are then provided to a manufacturing plant to construct a one-piece composite golf club shaft with preferred flexural and torsional stiffness distributions. This shaft can be achieved through a combination of prepreg layups, orientation of individual layers and / or sheets, fiber material properties, and / or resin content and material properties, to name just a few. Therefore, the present invention includes a one-piece golf club shaft incorporating any of the disclosed flexural or torsional stiffness distributions, which in one embodiment tapers uniformly over at least 70% of the shaft length, and in further embodiments completely lacks any conventional shaft "steps," wherein the outer diameter variation exceeds 1 mm.

[0154] Furthermore, some disclosed embodiments focus on a connector 3000 configured to releasably engage the root portion 1000 and the tip portion 2000, while another series of embodiments may incorporate a mid-section portion and a second connector. In these embodiments, connector 3000 releasably engages the tip portion 2000 and the mid-section portion, while the second connector releasably engages the mid-section portion and the root portion 1000. In one embodiment, the bending stiffness and torsional stiffness of the mid-section portion vary by less than 70% over a portion of the shaft located between the connectors, less than 60% in another embodiment, and less than 50% in yet another embodiment. However, in another embodiment, the bending stiffness varies by at least 5% over a portion of the shaft located between the connectors, at least 10% in another embodiment, and at least 15% in yet another embodiment. These embodiments selectively design stiffness abrupt changes over a relatively short length within a specific region to further achieve ideal inflection point positioning. This contrasts with conventional shaft designs that strive for a smooth stiffness transition throughout the entire length and describe abrupt stiffness changes as undesirable. Furthermore, for some swing types, abrupt changes in stiffness over a relatively short length within a specific area result in more efficient energy transfer.

[0155] In one such embodiment, the bending stiffness of the rod at the second connector exceeds 125 N*m over a distance no longer than 15% of the rod length 130. 2 The torsional stiffness of the shaft exceeds 100 N*m at a distance no longer than 15% of the shaft length of 130 mm. 2 In a further embodiment, the bending stiffness of the rod at the second connector exceeds 150 N*m over a distance not exceeding 15% of the rod length 130. 2The torsional stiffness of the shaft exceeds 115 N*m over a distance no longer than 15% of the shaft length of 130 mm. 2 Other embodiments recognize the minimum distance at which the aforementioned stiffness abrupt change occurs. For example, in these embodiments, the disclosed stiffness level is not limited to occurring at a distance not exceeding 15% of the shaft length 130, but must also occur at a distance of at least 3.5% of the shaft length 130 in these embodiments and at least 5% in other embodiments. The shaft 100 may also include a second reinforcing region located between a first point 5" from the distal end (110) of the shaft and a second point 36" from the distal end (110) of the shaft, wherein the shaft bending stiffness at a location within the second reinforcing region is (A) at least 100% greater than the minimum first tip bending stiffness and the minimum second tip bending stiffness, and (B) at least 50% greater than the minimum root bending stiffness. In another embodiment, the shaft bending stiffness at a location within the second reinforcing region is (A) at least 125 N*m. 2 (B) is at least 200% greater than both the minimum first tip portion bending stiffness and the minimum second tip portion bending stiffness, and (C) is at least 75% greater than the minimum root portion bending stiffness.

[0156] In a further embodiment, at least one of the tip or root portions includes a portion with filler material such that the cross-section perpendicular to the shaft axis is completely occupied by the filler material. This does not mean that the filler material may not contain voids or air pockets, as it does in some embodiments. The tip, root, or hollow portion of the entire shaft may be partially or completely filled with an elastic polymer or highly elastic material (e.g., viscoelastic urethane polymer), thermoplastic high elastic material (TPE), thermoplastic polyurethane (TPU), and / or other suitable types of material to dampen, isolate vibrations, and / or reduce noise. Another embodiment incorporates a polymer material, such as an ethylene copolymer, to dampen, isolate vibrations, and / or reduce noise when the golf club head strikes the golf ball. Examples include high-density ethylene copolymer ionomers, modified fatty acid ethylene copolymer ionomers, highly amorphous ethylene copolymer ionomers, ethylene copolymers of ethylene acrylate terpolymers, ethylene copolymers including magnesium ionomers, injection-moldable ethylene copolymers that can be used in conventional injection molding equipment to create various shapes, ethylene copolymers that can be used in conventional extrusion equipment to create various shapes, and / or ethylene copolymers having high compressibility and low elasticity similar to thermoset polybutadiene rubber. Further examples may incorporate a polymeric material and multiple microbubbles made of glass, ceramic, and / or plastic, also referred to herein as micro-hollow beads. When incorporated with the polymeric material, the microbubbles serve two purposes: (1) to replace the elastomer with air to reduce the overall filler weight, thereby reducing the specific gravity of the material; and (2) to increase the porosity of the filler material, allowing the formation of micropores in the polymeric material. Micropores are small cavities that allow the polymer to bend while maintaining the sound optimizations provided by the polymer itself, such as reduced decibel levels and sound duration. The polymeric material is preferably an elastomer, such as polyurethane or silicone resin with a Poisson's ratio of 0.00-0.50, or more preferably 0.40-0.50, while the microbubbles are preferably measured in D50 micrometers, which is the medium particle size of the sample being measured, with each microbubble having a diameter of approximately 18-50 micrometers. In one embodiment, the Shore hardness of the filler material is in the range of approximately A20 to D90. For example, the filler material may be an acrylic epoxy resin. Other filler material embodiments include polyurethane rubber, polyurethane, ionomers, elastomers, silicone resins, rubber, and other similar materials. Further embodiments incorporate filler materials with a hardness less than that of the tip or root portion, and optionally include elastic materials such as polymeric materials, natural or synthetic rubber, polyurethane, thermoplastic polyurethane (TPU), open-cell or closed-cell foams, silicone, metal foams, viscoelastic materials, or resins. In one embodiment, the density of the filler material is less than 0.9 g / cc, and in other embodiments less than 0.75 g / cc, 0.60 g / cc, and 0.45 g / cc.

[0157] Numerous modifications, alterations, and variations of the preferred embodiments disclosed herein will be apparent to those skilled in the art, all of which are contemplated and envisioned as being within the spirit and scope of the invention. For example, although specific embodiments have been described in detail, those skilled in the art will understand that the foregoing embodiments and variations can be modified to incorporate various substitutes and / or additional or alternative materials, relative arrangements of elements, and dimensional configurations. Therefore, although only a few variations of the invention have been described herein, it should be understood that the practice of these additional modifications and variations, and their equivalents, is within the spirit and scope of the invention as defined by the following claims. All devices or steps in the following claims, plus the corresponding structures, materials, actions, and equivalents of the functional elements, are intended to include any structures, materials, or actions for performing functions in combination with other claimed elements, as particularly claimed.

Claims

1. A golf club shaft, comprising: The shaft has a shaft distal end, a shaft proximal end, a shaft outer diameter, a shaft length, a shaft mass, a shaft center of gravity located at a distance from the shaft center of gravity at the shaft proximal end, and a turning point located at a distance from the turning point at the shaft proximal end, wherein each point along the shaft length has (i) a shaft bending stiffness including the maximum shaft bending stiffness, and (ii) a shaft torsional stiffness including the maximum shaft torsional stiffness; The shaft has a root portion that is joined to a tip portion by a connector, wherein the connector has a connector mass not exceeding 15% of the shaft mass. The root portion has a distal end, a proximal end, a root portion length of 20-40 inches, and a root portion mass of no more than 60 grams. The tip portion has a distal tip portion, a proximal tip portion, a tip portion length, and a tip portion mass, wherein the tip portion length is (a) 8-26 inches, (b) at least 25% of the root portion length, and (c) at least 20% of the shaft length, and the tip portion mass is no more than 35 grams and less than 75% of the root portion mass; The root portion is formed of root portion material having root material density, root portion mass, root portion elastic modulus and root portion shear modulus, and at each point along the length of the root portion having (i) root portion area moment of inertia, (ii) root portion polar moment of inertia, (iii) root portion bending stiffness and (iv) root portion torsional stiffness, the root portion bending stiffness including average root portion bending stiffness, maximum root portion bending stiffness and minimum root portion bending stiffness, the root portion torsional stiffness including average root portion torsional stiffness, maximum root portion torsional stiffness and minimum root portion torsional stiffness; The tip portion is formed of a tip portion material having a tip portion material density, a tip portion elastic modulus, and a tip portion shear modulus, and has (i) a tip portion area moment of inertia, (ii) a tip portion polar moment of inertia, (iii) a tip portion bending stiffness, and (iv) a tip portion torsional stiffness at each point along the length of the tip portion, the tip portion bending stiffness including an average tip portion bending stiffness, a maximum tip portion bending stiffness, and a minimum tip portion bending stiffness, the tip portion torsional stiffness including an average tip portion torsional stiffness, a maximum tip portion torsional stiffness, and a minimum tip portion torsional stiffness; in: The average bending stiffness of the tip portion is 10-50 N*m. 2 The average torsional stiffness of the tip portion is 5-40 N*m. 2 ; as well as The bending stiffness of the portion of the shaft located 5-36 inches from the proximal end of the shaft is at least 100% greater than the bending stiffness of the smallest tip portion.

2. The golf club shaft of claim 1, wherein the tip portion weighs no more than 30 grams, the tip portion weighs less than 70% of the root portion, and the connector weighs no more than 60% of the tip portion.

3. The golf club shaft according to claim 2, wherein the mass of the tip portion is no more than 25 grams, and the mass of the tip portion is less than 60% of the mass of the root portion.

4. The golf club shaft according to claim 2, wherein the maximum bending stiffness of the shaft does not exceed 300 N*m. 2 The maximum torsional stiffness of the rod does not exceed 250 N*m. 2 .

5. The golf club shaft according to claim 4, wherein the maximum bending stiffness of the shaft does not exceed 250 N*m. 2 The maximum torsional stiffness of the rod does not exceed 200 N*m. 2 .

6. The golf club shaft of claim 4, wherein the tip portion has a mass of 20-30 grams and the mass of the tip portion does not exceed 70% of the mass of the root portion.

7. The golf club shaft of claim 4, wherein the tip portion weighs no more than 20 grams.

8. The golf club shaft of claim 4, wherein the mass of the tip portion does not exceed 60% of the mass of the root portion.

9. The golf club shaft of claim 8, wherein the mass of the tip portion is at least 35% of the mass of the root portion.

10. The golf club shaft of claim 4, wherein the distance from the center of gravity of the shaft does not exceed 65% of the shaft length.

11. The golf club shaft of claim 10, wherein the distance from the center of gravity of the shaft does not exceed 55% of the shaft length.

12. The golf club shaft of claim 4, wherein the bending stiffness of the portion of the shaft located 5-36 inches from the proximal end of the shaft is at least 200% greater than the bending stiffness of the smallest tip portion.

13. The golf club shaft of claim 12, wherein the bending stiffness of the portion of the shaft located 5-36 inches from the proximal end of the shaft is at least 50% greater than the bending stiffness of the minimum root portion.

14. The golf club shaft of claim 12, wherein the bending stiffness of the portion of the shaft located 5-36 inches from the proximal end of the shaft is at least 125 N*m. 2 .

15. The golf club shaft of claim 14, wherein the bending stiffness of the shaft for a portion not exceeding 15% of the shaft length exceeds 125 N*m. 2 .

16. The golf club shaft of claim 4, wherein the turning point is within 6 inches of the portion of the connector.

17. The golf club shaft according to claim 4, wherein the average root portion bending stiffness is 50-110 N*m. 2 The average torsional stiffness of the root portion is 20-70 N*m. 2 The average bending stiffness of the tip portion does not exceed 40 N*m. 2 .

18. The golf club shaft of claim 4, wherein the length of the tip portion does not exceed 75% of the length of the root portion, and the average bending stiffness of the tip portion is not greater than 35 N*m. 2 The average root bending stiffness is 60-100 N*m. 2 The average torsional stiffness of the root portion is 25-60 N*m. 2 .

19. The golf club shaft of claim 4, wherein the bending stiffness of the portion of the shaft located 5-36 inches from the proximal end of the shaft is at least 50% greater than the bending stiffness of the minimum root portion.

20. The golf club shaft of claim 4, wherein the root portion has a mass of at least 40 grams.

21. The golf club shaft of claim 20, wherein the root portion weighs no more than 50 grams.

22. The golf club shaft of claim 21, wherein the root portion is 26-36 inches long and the tip portion is 10-22 inches long.

23. The golf club shaft of claim 4, wherein the coupling comprises a thermoplastic material.

24. The golf club shaft of claim 4, wherein the connector comprises a fiber-reinforced composite material.

25. The golf club shaft of claim 4, wherein the bending stiffness of the shaft remains constant at least 10% of the shaft length.

26. The golf club shaft of claim 4, wherein the shaft tapers uniformly over at least 70% of its length, and the connector portion is tapered.

27. A golf club shaft, comprising: The shaft has a shaft distal end, a shaft proximal end, a shaft outer diameter, a shaft length, a shaft mass, a shaft center of gravity located at a distance from the shaft center of gravity at the shaft proximal end, and a turning point located at a distance from the turning point at the shaft proximal end, wherein each point along the shaft length has (i) a shaft bending stiffness including the maximum shaft bending stiffness, and (ii) a shaft torsional stiffness including the maximum shaft torsional stiffness; The shaft has a root portion, which is connected to a tip portion via a connector; The root portion has a distal end, a proximal end, a root portion length of 20-40 inches, and a root portion mass of no more than 60 grams. The tip portion has a distal tip portion, a proximal tip portion, a tip portion length, and a tip portion mass, wherein the tip portion length is (a) 8-26 inches, (b) 25%-75% of the root portion length, and (c) at least 20% of the shaft length, and the tip portion mass is no more than 35 grams and less than 75% of the root portion mass; The root portion is formed of root portion material having root material density, root portion mass, root portion elastic modulus and root portion shear modulus, and at each point along the length of the root portion having (i) root portion area moment of inertia, (ii) root portion polar moment of inertia, (iii) root portion bending stiffness and (iv) root portion torsional stiffness, the root portion bending stiffness including average root portion bending stiffness, maximum root portion bending stiffness and minimum root portion bending stiffness, the root portion torsional stiffness including average root portion torsional stiffness, maximum root portion torsional stiffness and minimum root portion torsional stiffness; The tip portion is formed of a tip portion material having a tip portion material density, a tip portion elastic modulus, and a tip portion shear modulus, and has (i) a tip portion area moment of inertia, (ii) a tip portion polar moment of inertia, (iii) a tip portion bending stiffness, and (iv) a tip portion torsional stiffness at each point along the length of the tip portion, the tip portion bending stiffness including an average tip portion bending stiffness, a maximum tip portion bending stiffness, and a minimum tip portion bending stiffness, the tip portion torsional stiffness including an average tip portion torsional stiffness, a maximum tip portion torsional stiffness, and a minimum tip portion torsional stiffness; in: The average bending stiffness of the tip portion is 10-50 N*m. 2 The average torsional stiffness of the tip portion is 5-40 N*m. 2 ; The bending stiffness of the portion of the shaft located 5-36 inches from the proximal end of the shaft is at least 100% greater than the bending stiffness of the minimum tip portion and at least 50% greater than the bending stiffness of the minimum root portion. The maximum bending stiffness of the pole body shall not exceed 600 N*m. 2 The maximum torsional stiffness of the rod does not exceed 450 N*m. 2 .

28. The golf club shaft of claim 27, wherein the root portion weighs no more than 50 grams, the tip portion weighs no more than 30 grams, the connector weighs no more than 60% of the tip portion's weight, the tip portion is 10-22 inches long, and the root portion is 26-36 inches long.

29. The golf club shaft of claim 28, wherein the root portion weighs no more than 45 grams, the tip portion weighs no more than 25 grams, and the connector weighs 25%-75% of the tip portion.

30. The golf club shaft of claim 28, wherein the root portion has a mass of 40-50 grams, the tip portion has a mass of 20-30 grams, the tip portion has a length of 10-22 inches, and the root portion has a length of 26-36 inches.

31. The golf club shaft of claim 28, wherein the mass of the tip portion does not exceed 70% of the mass of the root portion.

32. The golf club shaft of claim 31, wherein the mass of the tip portion is 35%-60% of the mass of the root portion, and the connector has a connector mass of 5-17.5 grams.

33. The golf club shaft of claim 28, wherein the distance from the center of gravity of the shaft does not exceed 65% of the shaft length.

34. The golf club shaft of claim 33, wherein the distance from the center of gravity of the shaft does not exceed 55% of the shaft length.

35. The golf club shaft of claim 33, wherein the distance between the shaft's center of gravity and the proximal end of the shaft is greater than the distance between any part of the connector and the proximal end of the shaft.

36. The golf club shaft of claim 33, wherein the maximum shaft bending stiffness does not exceed 300 N*m. 2 The maximum torsional stiffness of the rod does not exceed 250 N*m. 2 .

37. The golf club shaft of claim 36, wherein the maximum bending stiffness of the shaft does not exceed 250 N*m. 2 The maximum torsional stiffness of the rod does not exceed 200 N*m. 2 .

38. The golf club shaft of claim 33, wherein the bending stiffness of the portion of the shaft located 5-36 inches from the proximal end of the shaft is at least 125 N*m. 2 It has a bending stiffness at least 200% greater than that of the minimum tip portion and at least 75% greater than that of the minimum root portion.

39. The golf club shaft of claim 38, wherein the bending stiffness of the shaft for a portion not exceeding 15% of the shaft length exceeds 125 N*m. 2 .

40. The golf club shaft of claim 39, wherein the bending stiffness of the shaft for at least 3.5% of its length exceeds 125 N*m. 2 .

41. The golf club shaft of claim 39, wherein the torsional stiffness of the portion of the shaft located 5-36 inches from the proximal end of the shaft is at least 100 N*m. 2 The torsional stiffness of the portion of the shaft not exceeding 15% of the shaft length exceeds 100 N*m. 2 .

42. The golf club shaft of claim 41, wherein the bending stiffness of said portion of the shaft exceeds 150 N*m. 2 The torsional stiffness of the rod body exceeds 115 N*m. 2 The density of the tip material is within 15% of the density of the root material.

43. The golf club shaft of claim 28, wherein the turning point is within 6 inches of the portion of the connector.

44. The golf club shaft of claim 28, wherein the average root section bending stiffness is 50-110 N*m. 2 The average torsional stiffness of the root portion is 20-70 N*m. 2 .

45. A golf club shaft system, comprising: A shaft having a distal end, a proximal end, an outer diameter, a length, and a mass, wherein each point along the length of the shaft has (i) a bending stiffness and (ii) a torsional stiffness. The shaft has a root portion that is releasably engaged by a connector to a tip portion selected from at least a first tip portion and at least a second tip portion, wherein the connector has a connector mass. The root portion has a distal end, a proximal end, and a length; The first tip portion has a first tip portion distal end, a first tip portion proximal end, a first tip portion length less than the length of the root portion, and a first tip portion mass; The second tip portion has a second tip portion distal end, a second tip portion proximal end, a second tip portion length less than the length of the root portion, and a second tip portion mass; The root portion is formed of root portion material having root material density, root portion mass, root portion elastic modulus and root portion shear modulus, and has (i) root portion area moment of inertia, (ii) root portion polar moment of inertia, (iii) root portion bending stiffness and (iv) root portion torsional stiffness at each point along the length of the root portion. The first tip portion is formed of a first tip portion material having a first tip portion material density, a first tip portion elastic modulus and a first tip portion shear modulus, and has (i) a first tip portion area moment of inertia, (ii) a first tip portion polar moment of inertia, (iii) a first tip portion bending stiffness and (iv) a first tip portion torsional stiffness at each point along the length of the first tip portion. The second tip portion is formed of a second tip portion material having a second tip portion material density, a second tip portion elastic modulus and a second tip portion shear modulus, and has (i) a second tip portion area moment of inertia, (ii) a second tip portion polar moment of inertia, (iii) a second tip portion bending stiffness and (iv) a second tip portion torsional stiffness at each point along the length of the second tip portion. At least one of the following is true: (a) the bending stiffness of the largest second tip portion is at least 25% greater than that of the largest first tip portion; (b) the torsional stiffness of the largest second tip portion is at least 35% greater than that of the largest first tip portion. The mass of the second tip portion is no more than 50% greater than the mass of the first tip portion; The average bending stiffness of the first tip portion is 10-50 N*m. 2 The average bending stiffness of the second tip is 10-50 N*m. 2 ;as well as The average torsional stiffness of the first tip portion is 5-40 N*m. 2 The average torsional stiffness of the second tip is 5-40 N*m. 2 .

46. ​​The golf club shaft system of claim 45, wherein the bending stiffness of the largest second tip portion is at least 50% greater than the bending stiffness of the largest first tip portion, and the torsional stiffness of the largest second tip portion is at least 75% greater than the torsional stiffness of the largest first tip portion.

47. The golf club shaft system of claim 46, wherein the bending stiffness of the largest second tip portion is 50%-150% greater than that of the largest first tip portion, and the torsional stiffness of the largest second tip portion is 75%-350% greater than that of the largest first tip portion.

48. The golf club shaft system of claim 45, wherein the mass of the connector does not exceed (a) the mass of the first tip portion or (b) the mass of the second tip portion.

49. The golf club shaft system of claim 48, wherein the mass of the connector is at least 25% of (a) the mass of the first tip portion and (b) the mass of the second tip portion.

50. The golf club shaft system of claim 45, wherein the length of the first tip portion is at least 25% shorter than the length of the root portion, and the length of the second tip portion is at least 25% shorter than the length of the root portion.

51. The golf club shaft system of claim 45, wherein the shaft has a first shaft center of gravity located at a distance from the proximal end of the shaft when the first tip portion is installed, the first shaft center of gravity distance not exceeding 65% of the shaft length, and the shaft has a second shaft center of gravity located at a distance from the proximal end of the shaft when the second tip portion is installed, the second shaft center of gravity distance not exceeding 65% of the shaft length.

52. The golf club shaft system of claim 51, wherein the length of the first tip portion is 25%-80% shorter than the length of the root portion, and the length of the second tip portion is 25%-80% shorter than the length of the root portion.

53. The golf club shaft system according to claim 51, wherein the distance between the center of gravity of the first shaft and the distance between the center of gravity of the second shaft differs by no more than 5 mm.

54. The golf club shaft system of claim 45, wherein (a) the torsional stiffness of the largest first tip portion is greater than the bending stiffness of the largest first tip portion, and (b) the torsional stiffness of the largest second tip portion is less than the bending stiffness of the largest second tip portion.

55. The golf club shaft system of claim 54, wherein (a) the torsional stiffness of the largest first tip portion is at least 30% greater than the bending stiffness of the largest first tip portion, and (b) the torsional stiffness of the largest second tip portion is at least 50% less than the bending stiffness of the largest second tip portion.

56. The golf club shaft system of claim 55, wherein the second tip portion is no more than 20% heavier than the first tip portion, the first tip portion is 35%-85% of the root portion's mass, and the second tip portion is 35%-85% of the root portion's mass.

57. The golf club shaft system of claim 45, wherein the bending stiffness of the shaft exceeds 125 N*m over a distance not exceeding 15% of the shaft length. 2 The torsional stiffness of the pole exceeds 100 N*m over a distance not exceeding 15% of the pole length. 2 .

58. The golf club shaft system of claim 45, wherein the root portion material is non-metallic, and at least one of the first tip portion material and the second tip portion material is non-metallic.

59. The golf club shaft system of claim 45, wherein the mass of the root portion is 35%-75% of the shaft mass, the density of the first tip material is within 15% of the density of the root material, and the density of the second tip material is within 15% of the density of the root material.

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