Shaft Structure with Configurable Bending, Weight, Moment-of-Inertia and Torque Profile

Abstract

A shaft structure with a configurable bending, weight, torque and moment-of-inertia profile is provided for golf clubs, fishing rods, and the like. The shaft structure employs an innovative inner and outer shaft structure. The golfer, in practice, configures the profile of a golf shaft by choosing from a plurality of different inner shaft structures each having a unique bending, weight, moment-of-inertia and torque profile. The inner shaft is securely fastened within the outer shaft. The combination of the inner shaft with the outer shaft results in an advantageous bending, weight, torque and moment-of-inertia profile. The golfer can, at any time and very easily, change the profile of the golf shaft according to their physical, course and weather conditions for any given day.

Description

FIELD OF THE INVENTION

This invention relates to shafts for golf clubs, fishing rods and the like and more particularly where the overall bending, weight, torque and moment-of-inertia profiles of these devices can be configured by the user to match their physical abilities as well as course and weather conditions.

BACKGROUND OF THE INVENTION

Golf shafts are typically manufactured with a predetermined bending, weight, torque and moment-of-inertia profile. The “bending profile” of a golf shaft refers to a distinct flex pattern that a conventional golf shaft exhibits when subjected to a force. The flex pattern is typically measured as the amount of deflection the shaft experiences when the shaft is positioned horizontally and subjected to a constant force.

Previous knowledge of golf shaft dynamics resulted in a general understanding that the overall stiffness of a golf shaft played a role in the performance of a golf club. However, it has been discovered that the overall bending profile of the shaft has much more to do with the performance of a golf club than merely its overall stiffness. The bending profile directly contributes to ball launch angle and spin, both of which can directly affect shot distance and accuracy. Additionally, the bending profile can influence club-head reaction and orientation before the clubface makes contact with the ball. Presently, golf shafts are mass produced with a predefined and fixed bending profile without regard for a golfer's individual swing mechanics. Typically, these parameters are designed in an attempt to accommodate a vast multitude of golfers.

Prevailing weather conditions can also affect optimum ball flight. For example, on a windy day, a golfer might choose to reconfigure their shaft for a bending profile that promotes a lower penetrating ball flight which reduces the affects of the wind. Conversely, on a day with little or no wind, a golfer may choose to configure the bending profile to promote a higher launch angle.

Course conditions can also dictate shot choice and performance. On a course with narrow fairways a golfer may choose a stiffer shaft so as to improve accuracy whereas a course that has wider fairways but is longer would dictate a less stiffer shaft so as to maximize distance.

The overall weight of a golf shaft plays a crucial part in the performance of the golf club. The lighter the golf shaft the more head speed a golfer can generate which translates into more distance. However, some golfers find that a lighter shaft does not allow them to “feel” the position of the head through the swing and as result there is a loss of control. Therefore, some golfers prefer a heavier golf shaft. The weight of the golf shaft is a function of a golfer's preferences and can enhance performance.

The torque of a golf shaft directly relates to the performance of a golf shaft. Torque is generally defined as torsional resistance. As such, torque also relates to the amount and type of feedback the golfer receives when the golf ball is struck. A golf ball which strikes the toe or the heel of the golf club causes the golf club head to rotate about its center of gravity. This action causes the golf ball to drastically alter course from the intended target line. Additionally, off center hits generate vibrational energy that is then transmitted via the golf shaft to the golfer's hands resulting in a “stinging” sensation. Golf shafts with a relatively high torque rating can cause the golf club head to rotate more thereby less energy is translated into vibrational energy. As a result less vibrational energy is transmitted to the golfer's hands. Conversely, a golf shaft that has a low torque rating necessarily causes the golf club head to rotate less thereby more energy is converted to vibrational energy which is then transmitted to the golfer's hands. The torque of the golf shaft is a function of a golfer's preferences and can enhance performance.

The moment-of-inertia of a golf club can be directly attributable to the “feel” of the golf club and with that the performance by increasing the confidence level of the golfer. In lieu of configuring a moment-of-inertia the golfer may choose to configure the swing-weight of the golf club as indicated by a swing-weight machine.

Various proposals to provide variable stiffness for a golf club shaft (or even a fishing pole) have previously been made that involve using a hollow shaft charged with a gas or liquid fluid that can be pressurized and by mechanical devices such as rods, jackscrews and the like. Increasing the fluid pressure in the shaft increases the shaft stiffness. Increasing the length of the rod increases the tension and hence shaft stiffness.

Such pressurizable shafts are illustrated, for example, by Menzies U.S. Pat. No. 1,831,255, Sears U.S. Pat. No. 2,432,450, Busch U.S. Pat. No. 3,037,775, Burrough U.S. Pat. No. 4,800,668 (a fishing rod), Simmons U.S. Pat. No. 5,316,300, Koch et al. U.S. Pat. No. 5,540,625, Painter U.S. Pat. No. 5,632,693 and Qualizza U.S. Pat. No. 7,226,365.

So far as is known, these variable stiffness, hollow shaft structures of the prior art do not address changing a shaft's bending profile but rather have defined a device which indiscriminately promotes a stiffness change across the entire shaft and never addresses the ability to adjust the bending characteristics of the golf shaft. Additionally, the prior art does not address being able to change a shaft's overall weight, torque or moment-of-inertia.

SUMMARY OF THE INVENTION

In order for a golf club to be effective and ultimately configured for a golfer by the golfer without requiring the golfer to have intimate knowledge or club-building skills, the present invention provides for a device that can be easily changed to accommodate the golfer's abilities, weather and course condition for any given day. The device can also be adapted for use in existing golf shafts.

The present invention overcomes the inability of prior art shafts to create a unique bending, weight, torque and moment-of-inertia profile. The present invention also overcomes the inability of the prior art to be able to effect a change in the performance of the golf shaft by providing a device which does not serve to present an axial stress force to a conventional shaft but rather provides a device which combines a shaft-in-a-shaft structure where an outer shaft is complimented by an inner, configurable bending, weight, torque and moment-of-inertia profile shaft. The inner shaft structure is placed within an outer shaft structure, in effect forming a shaft within a shaft. The bending, weight, torque and moment-of-inertia profile of the overall shaft structure is born form the compounded action of both the inner and outer shaft structures. Given this arrangement, new shafts as well as existing shaft's bending, weight, torque and moment-of-inertia profiles can be readily changed that will match the golfer's abilities so as to maximize both shot accuracy and distance.

The inner shaft structure can easily be exchanged with another thereby in effect changing the overall shaft bending, weight, torque and moment-of-inertia profile. Each unique inner shaft structure has a unique bending, weight, weight distribution and torque rating. The configurable profile shaft does not require special tools or skills to affect the configuration of the bending, weight, moment-of-inertia or torque profile of an overall shaft structure.

By choosing different inner shaft structures with each having their own bending, weight, weight distribution and torque parameters, an overall shaft structure can be built by the golfer to accommodate their individual physical abilities as well as to match course and weather conditions for an individual day. In practice, the golfer extracts the inner shaft structure from the outer shaft structure, chooses a new inner shaft structure and then securely places the inner shaft structure back within the outer shaft structure.

An object of the present invention is to provide an overall shaft structure which allows a golfer to change the bending profile of a golf shaft to suit their needs, physical abilities, course and weather conditions.

Another object of the present invention is to provide an overall shaft structure which allows a golfer to change the overall weight of a golf shaft to suit their needs, physical abilities, course and weather conditions.

Yet another object of the present invention is to provide an overall shaft structure which allows a golfer to change the moment-of-inertia of the shaft structure and hence “feel” of a golf club to suit their preferences.

Another object of the present invention is to provide an overall shaft structure which allows a golfer to change the torque of a golf shaft to suit their preferences and physical needs.

Another object of the present invention is to provide a shaft structure that has a selectable bending profile. Hence, a single assembled shaft structure can replace many different combinations and permutations of golf shafts, golf clubs, fishing poles and manufacturing procedures and can avoid the need for large inventories of golf clubs with golf club shafts pre-set to different stiffness values, thereby effecting a saving of what would otherwise be an expenditure of substantial amounts of money.

Another object of the present invention is to provide a shaft structure which allows a golfer to customize the bending profile of each shaft of an entire set of clubs, or of fishing poles, according to his ability or wishes without being dependent upon the shaft stiffness, weight, torque and moment-of-inertia that happens as a result from shaft manufacturing procedures as in the prior art.

Yet another object of the current invention is to provide a device which can be easily adapted to an existing shaft structure so as to provide a golfer the ability to adjust the bending profile of their existing golf shaft.

Yet another object of the current invention is to provide a device which can be easily adapted to an existing shaft structure so as to provide a golfer the ability to adjust the moment-of-inertia profile of their existing golf shaft to match that of their favorite club. Therefore, all the clubs in the bag can have the same “feel” as their favorite club.

Another object of the present invention is to provide a fishing rod structure which allows a fisherman to configure the bending profile a fishing rod.

Another object of the current invention is to provide for a device that can easily replicate the physical and hence performance characteristics of any given shaft on the market. If a golfer chooses they or a manufacturer of the current invention can interrogate other golf shafts on the market in order to gather the variable bending, weight, moment-of-inertia and torque characteristics of the shaft. In this manner the resultant behavioral characteristics can be duplicated by the present invention. As such the present invention can replicate the performance of virtually any other shaft on the market.

Other and further objects, aims, features, advantages, applications, embodiments and the like regarding the present invention will be apparent to those skilled in the art from the present specification, attached drawings, and appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention may be understood by reference to the following description taken in conjunction with the accompanying drawings, in which, like reference numerals identify like elements, and in which:

FIG. 1 illustrates a perspective view of one embodiment of a golf club which incorporates a shaft structure of the present invention;

FIG. 2 illustrates a view of the proximal end of inner shaft structure of the shaft structure of FIG. 1;

FIG. 3 illustrates a more detailed view of the inner shaft structure of the shaft structure of FIG. 1;

FIG. 4 illustrates a cross-sectional view of the connection apparatus of the coupling section of the shaft structure shown in FIG. 3;

FIG. 5 view of the distal end of inner shaft structure of the shaft structure of FIG. 1;

FIG. 6 illustrates an alternative embodiment of the current invention that reveals segmented inner shaft structure;

FIG. 7 illustrates a cross-sectional view of the segments of the shaft structure shown in FIG. 6;

FIG. 8 illustrates a locking mechanism of the shaft structure shown in FIG. 6;

FIG. 9 illustrates the nomenclature for displaying stiffness, weight and torque for a segment for the shaft structure shown in FIG. 6;

FIG. 10 illustrates an alternative embodiment of the current invention using separate components for the bending profile, weight, weight distribution and torque;

FIG. 11 illustrates yet another embodiment of the current invention whereby the inner and outer shaft structures are in full contact in effect forming one shaft with out the need for spacers;

FIG. 12 illustrates another alternative embodiment of the current invention that utilizes a thin layer of fluid to transmit the bending profile of the outer shaft structure to the inner shaft structure.

DETAILED DESCRIPTION

FIG. 1 reveals an illustrative golf club 10 that incorporates an embodiment of an overall shaft structure 12 of the present invention. In the preferred embodiment, overall shaft structure 12 includes an outer shaft structure 18 and an inner shaft structure 16. Both the outer shaft structure 18 and the inner shaft structure 16 are defined by a proximal and distal end. In the matter of a golf club the proximal end is accompanied by a conventional golf grip 25 whereas the distal end is accompanied by a conventional golf club-head 30. Shaft structure 12 is defined as having an overall unique bending, weight, moment-of-inertia and torque profile. The overall moment-of-inertia of shaft structure 12 is defined by the unique distribution of weight of both the outer shaft structure 18 and the inner shaft structure 16. The bending, weight, weight distribution and torque profile of the outer shaft structure 18 remains constant and fixed. The inner shaft structure 16 exhibits a bending, weight, weight distribution and torque profile as well but can be exchanged with a different inner shaft structure 16 that exhibits a different bending, weight, weight distribution and torque profile thereby in effect allowing the golfer to modify the profile of the shaft structure 12 to their preference. Both outer shaft structure 18 and inner shaft structure 16 can be fashioned from graphite, ferrous and non-ferrous metals, plastics and the like and need not be of the same material. Those skilled in that art will recognize that a vast multitude and combinations of materials may be used for both the outer shaft structure 18 and the inner shaft structure 16 and that the use of alternate materials does not deviate from the scope or the spirit of the present invention.

In the present invention both the outer shaft structure 18 and inner shaft structure 16 exhibit a bending profile that is defined by a unique pattern of stiffness that traverses the inner shaft structure 16 from the proximal end to the distal end longitudinally. The pattern of stiffness allows for a unique bending pattern for shaft structure 12 that is born from the convoluted bending patterns of the inner shaft structure 16 and outer shaft structure 18 which are in mechanical cooperation. The outer shaft structure 18 is defined by a stiffness pattern that may be constant from proximal to distal end or in other embodiments it may change. In the preferred embodiment the inner shaft structure 16 has a stiffness pattern that changes from proximal to distal end. In another embodiment and with an existing golf shaft 12 the outer shaft structure 18 stiffness varies and defines the bending pattern. In this mode the inner shaft structure 16 bending profile would be profiled as a constant stiffness from proximal to distal end. As a result the overall bending profile would remain constant but the stiffness would increase. Those skilled in the art will recognize that a multitude of combinations of bending patterns can occur for the inner shaft structure, outer shaft structure or both and that these various combinations do not deviate from the spirit or scope of the present invention. This pattern defines, among other things, the kick-point of the overall shaft structure 12. As is well known in the industry the kick-point of the overall shaft structure 12 is a major determinant in golf ball trajectory. For instance, a high kick-point will cause a low golf ball trajectory while a low kick-point will cause a high golf ball trajectory. A mid kick-point will cause a mid golf ball trajectory.

In the present invention the overall weight of the shaft structure 12 is defined by the weight of the outer shaft structure 18 in additive combination with the weight of the inner shaft structure 16. The weight of the shaft structure 12 plays an important role in the performance of a golf club 10 whereas a lighter overall shaft structure 12 weight allows the golfer to swing the golf club 10 faster thereby increasing club-head 30 speed which translates into more distance. Although a heavier shaft structure 12 and hence a heavier golf club 10 allows for less club-head 30 speed there is a benefit that relates to accuracy derived from being able to better control the golf club 10 due to the lower swing speed. Additionally, as the golfer becomes older he or she can regain swing-speed by making the overall shaft structure 12 lighter by exchanging the inner shaft structure 16 with one that has less weight thereby reducing the overall weight of the golf club 10.

In the present invention the weight profile or rather the distribution of weight longitudinally is defined by the distribution of weight of the outer shaft structure 18 in additive combination with the distribution of weight of the inner shaft structure 16. The weight distribution of the outer shaft structure 18 may be constant from proximal to distal end or in other embodiments it may change. The weight distribution of the inner shaft structure 16 is unique and can be distributed so as to effect the overall moment-of-inertia of the golf club 10. In another embodiment and with an existing golf shaft 12 the outer shaft structure 18 weight distribution varies. In this mode the inner shaft structure 16 weight distribution would be constant from proximal to distal end. As a result the overall weight of the shaft structure 12 would increase but not the distribution of weight. Those skilled in the art will recognize that a multitude of combinations of weight distributions can occur for the inner shaft structure, outer shaft structure or both and that these various distributions do not deviate from the spirit or scope of the present invention. In more generic terms the moment-of-inertia relates to the “feel” of the golf club 10 such as it is described by a golfer as the golf club 10 being “heavy” or “light”. A proxy for moment-of-inertia is swing-weight of the golf club 10 as is well known in the industry. In general terms the moment-of-inertia will increase when more weight is placed toward the distal end of the golf club 10 and will decrease as more weight is placed toward the proximal end. In this regard weight distribution within the inner shaft structure 16 can effect the moment-of-inertia.

The torque of a golf shaft 12 directly relates to the performance of a golf shaft 12. The torque profile of the outer shaft structure 18 is constant from proximal to distal end. The torque profile of the inner shaft structure 16 is unique and can be distributed so as to affect the torque profile of the overall shaft 12. As is well known torque relates to the amount and type of feedback the golfer receives when the golf ball is struck. Additionally, a golf ball which strikes the toe or the heel of the golf club 10 causes the golf club head 30 to rotate about its center of gravity. Off center hits also tend to generate vibrational energy that is then transmitted via the golf shaft 12 to the golfers hands resulting in a “stinging” sensation. Golf shafts 12 with a relatively high torque rating can cause the golf club head 30 to rotate more. As a result less vibrational energy is transmitted to the golfer's hands. Conversely, a golf shaft 12 that has a low torque rating necessarily causes the golf club head 30 to rotate less in which more energy is converted to vibrational energy and on to the golfer's hands. The torque of the golf shaft 12 is a function of a golfer's preference and can enhance performance.

In the preferred embodiment and referring to FIG. 2, inner shaft structure 16 includes select bending, weight, weight distribution and torque parameters and further includes a proximal and distal end. Inner shaft structure 16 is held in place at the proximal end by threaded cap 19. Threaded cap 19 cooperatively engages threaded cup 21 of outer shaft structure 18 which is firmly affixed to the inner diameter of outer shaft structure 18 by conventional means. The proximal end of inner shaft structure 16 includes disk 25. Disk 25 includes longitudinal lands 3 and 5 which cooperatively engage slots 7 and 9 respectively of threaded cup 21. The cooperative engagement of lands 3 and 5 with slots 7 and 9 serve to anchor the torque as it is transmitted from the golf club-head 30 to the inner shaft structure 16.

With reference to FIG. 3 inner shaft 16 is comprised of main body 22, spacer 15, spacer 17, and spacer 19. Main body 22 is designed so as to provide a distinct bending, weight, weight distribution and torque profile. The distinct bending pattern for main body 22 is driven from the material, diameter and wall thickness. Weight is a function of density of material and wall thickness. Torque is a function of material, diameter and wall thickness. Those skilled in the art will recognize that initially the bending, weight, weight distribution and torque profile are all co-dependent upon the material, wall thickness and diameter of the main body 22 of the inner shaft structure 16. As such the inner shaft structure 16 will be designed taking into account of the design parameters such as material type, wall thickness and diameter. Distal end of inner shaft structure 16 is comprised of coupler 26. In another embodiment an inner shaft structure system may be designed that incorporates a plurality of inner shaft structure such that each inner shaft structure would accommodate one or more particular parameters. For instance, there may be an inner shaft structure 16 for addressing the bending profile and another inner shaft structure 16 that would address weight distribution.

Spacers 15, 17 and 19 serve to support inner shaft structure 16 by virtue of mechanical communication with the outer shaft structure 18 at strategic locations. The number and placement of spacers 15, 17 and 19 are defined so as to transfer the bending pattern of the outer shaft structure 18, when under load, to the inner shaft structure 16. In this manner inner shaft structure 16 is then able to influence the bending profile of the overall shaft structure 12 by virtue of its configurable arrangement. Those skilled in the art will recognize that a multitude of different types and means of support and location may be provided and these alternative means and locations do not deviate from the scope or spirit of the present invention.

Referring to FIG. 4, male coupling device 28 of coupler 26 includes platen 23 and cross member 24. Platen 23 has a diameter that cooperates and is firmly affixed to the internal diameter of the distal end of inner shaft structure 16. Cross member 24 includes male cross pattern which cooperates and is received by the female cross pattern of the female coupling device 29. The diameter of the female coupling device 29 cooperates and is affixed to the inside diameter of outer shaft structure 18 by conventional means. Further, coupler 26 serves to convey the torque that is imposed by the club head 30 to inner shaft structure 16.

With further reference to FIG. 5 outer shaft structure 18 is affixed to the inside diameter of hosel 35 of club-head 30. Inner shaft structure 16 is placed within the outer shaft structure 18. Upon the introduction of inner shaft structure 16 to outer shaft structure 18 the golfer will choose to rotate the inner shaft structure 16 so as to align the cross member 24 of male coupling device 28 with female coupling device 29 of coupler 26. Once aligned the inner shaft structure 16 of the male coupling device 28 engages with female coupling device 29 thus allowing the inner shaft structure 16 to be fully seated. In this manner inner shaft structure 16 is allowed to “float” or move axially but yet still retain torque integrity generated at the club-head 30 due to the arrangement of coupler 26. Those skilled in the art will recognize that a multitude of designs can occur for the transferring of torque from the club head 30 to the outer shaft structure 18 and then to the inner shaft structure 16 and that these various other designs do not deviate from the spirit or scope of the present invention.

Female coupling device 29 receives and cooperates with male coupling device 28 to form a structurally sound mechanical detachably connection that, by design, structurally transitions, homogenously, the characteristic torque generated at the club-head 30 to the inner shaft structure 16. Male coupling device 28 and female coupling device 29 can be fabricated from lightweight material such as carbon fiber or ultra-high-molecular weight (UHMW) plastic.

FIG. 6 reveals an alternative embodiment including an outer shaft structure 18 and inner shaft structure 16 wherein inner shaft structure 16 is comprised of separate, mechanically connected sections. Each section may have a unique stiffness, weight and torque rating. Three separate sections 22, 23 and 24 are shown to illustrate the present invention. With respect to the inner shaft structure 16, section 22 is typically referred to as the tip section; section 23 is often referred to as the mid section and section 24 is often referred to as the butt section. Fewer or additional sections are within the scope of the present invention. Both the outer shaft structure 18 and inner shaft structure 16 may be formed from various materials such as graphite, ferrous and non-ferrous metals, plastics and the like. Those skilled in the art will recognize that a multitude of material can be used for both the inner shaft structure 16 and outer shaft structure 18 and using other materials does deviate from the spirit or scope of the present invention.

The variable bending profile of the overall shaft structure 12 includes the variable bending properties of both the inner shaft structure 16 and outer shaft structure 18 working in tandem. The overall bending profile of outer shaft 18 is substantially constant while the overall bending profile of the inner shaft structure 16 is modifiable by virtue of the stiffness contributions of each of the sections 22, 23 and 24.

The overall weight of shaft structure 12 includes weight of the outer shaft structure 18, which may be substantially constant, as well as the overall configurable weight contributed by assembled sections 22, 23 and 24 that define the inner shaft structure 16.

The moment-of-inertia of shaft structure 12 and as well the golf club 10 itself, includes the moment-of-inertia of the outer shaft structure 18, which is substantially constant, as well as the total configurable moment-of-inertia as contributed by the distribution of weight of assembled sections 22, 23 and 24 that define the inner shaft structure 16.

The overall shaft structure 12 is detachably affixed at one end of a conventional club head 30 (not detailed structurally) and at the opposite end with a circumferentially extending, conventional golf grip 25 (not detailed structurally).

With reference to FIG. 7, the proximal end of the mid section 23 is detachably engaged with coupler 26 and with coupler 31 at the distal end of the mid section 23. Tip section 22 may be detachably engaged at the proximal end of the tip section 24 with coupler 31 and by coupler 50 at the distal end of tip section 24. Inner shaft structure 16 is held in place at the distal end by the cooperative engagement of coupler 50. Those skilled in the art will recognize and appreciate that a plurality of sections as well as a plurality of different types of coupling devices can be incorporated and that such an arrangement does not deviate from the scope and the spirit of the present invention. Mechanical connection of the individual sections occurs via a quick disconnect coupler.

Spacers 15, 17 and 19 of section 22, 23 and 24 respectively serve to support inner shaft structure 16 relative to outer shaft structure 18 at strategic locations. The number and placement of spacers 15, 17 and 19 are defined so as to transfer the distinct bending pattern of the outer shaft structure 18, when under load, to the inner shaft structure 16. In this manner inner shaft structure 16 is then able to influence the bending profile of the overall shaft structure 12 by virtue of its configurable arrangement. Additionally, the length of tip section 22, mid section 23 and butt section 24 can be chosen to advantageously place the kick-point anywhere along the shaft. For instance, in addition to the stiffness chosen for mid section 23 mid section 23 can be configured to be exceptionally long with spacers 17 located near the ends of mid section 24 so that maximum bending would occur at mid shaft thereby creating a mid kick-point.

FIG. 8 reveals a typical quick disconnect coupler 35. Locking mechanism 35 including locking tab 36 cooperating with loading spring 37. Loading spring 37 is located within channel 38. As an example, during assembly of mid section 23 with butt section 24, the golfer introduces the male coupling device 28 to the female coupling device 29. Pushing down firmly causes locking tab 36 of locking mechanism 35 to retract into channel 38 thusly loading spring 37 and allowing cross member 34 to fully engage female coupling device 29. The pushing action causes locking tab 36 of locking mechanism 35 to retract into channel 38 thus granting the ability to fully insert male cross member 34 of male coupling device 28 into female coupling device 29. Both male coupling device 28 and female coupling device 29 become fully engaged when locking tab 36 of locking member 35 protrudes past the bottom of female coupling device 29. At this time, locking tab 36 springs back to the initial position and the top of locking tab 36 engages the bottom of female coupling device 29 thereby creating a detachable rigid and firmly affixed structural connection. Conversely, upon disassembly, the golfer inserts special tool 50 into acceptance hole 52. Upon activation of the tool, scrawl end 54 inserts into acceptance hole 52 and reaches locking tab 36. Further prosecution of the scrawl end 54 inward causes locking tab 36 to retract into channel 37 thereby compressing spring device 37. When locking tab 36 is fully retracted into channels 38 the golfer is than able to disconnect mid section 23 from butt section 24.

FIG. 9 depicts a typical mid section 23 that displays markings 70 that identify the particular characteristics of stiffness, weight and torque. The stiffness marking 72 refers to the stiffness of mid section 23 in a 200 to 300 scale with 300 being the stiffest. The weight marking 74 refers to the overall weight of the mid section 23 in grams, i.e. 30 grams. The torque marking 76 of the mid section 23 is depicts as 1.0 to 5.0 scale where 1.0 equals the lowest torque while 5.0 represents the highest torque rating of the tip section 23. Those skilled in the art will appreciate that any marking nomenclature such as color-coding and other decipherable markings could be use in lieu of the enclosed markings and that doing so will not deviate from the teachings herein. In practice, a golfer would have a multitude of sections 22, 23 and 24 as spares and then would choose the sections that would best obtain the performance that they are looking for.

Configuring a variable bending profile is defined by the choice and then detachable assembly of tip section 22, mid section 23 and butt section 24. For instance, a golfer may choose a bending profile that promotes a strong mid section 23 and butt section 24 with a weak tip section 22. This arrangement would facilitate a low kick-point. In this manner tip section 22 would be chosen with the lowest stiffness rating as compared to mid section 23 and butt section 24. Mid section 23 and butt section 24 would be chosen with a higher stiffness than tip section 22. Conversely, if a golfer chooses to configure a bending profile with a mid kick-point then the golfer would choose a mid section 23 with stiffness rating that is lower than tip section 22 and butt section 24. As well choosing a high kick-point would dictate that the golfer would choose a butt section 24 with stiffness rating that is less than the stiffness rating for tip sections 22 and mid section 23. It should be noted that the overall stiffness as defined by the contribution of the assembled tip section 22, mid section 23 and butt section 24 constitute a stiffness profile.

Additionally, in practice, the golfer would decide upon an overall target weight of the golf shaft 12. The golfer would then choose the weight of each section which has the required stiffness so that the total combined weight of the assembled inner shaft structure 16 in conjunction with the weight of the outer shaft structure 18 would achieve the desired target weight of the overall golf shaft 12.

In addition to choosing the correct overall weight the golfer would also choose which section 22, 23 or 24 would contribute the greater weight to the overall weight of the inner shaft structure 16 such that the placement of the weight would cause the moment-of-inertia to be to their liking. For instance, if a golfer chooses to decrease the moment-of-inertia they would choose a butt section 24 whose weight is greater than tip section 22 and mid section 23. Conversely, if they choose to increase the moment-of-inertia they would necessarily choose a tip section 22 weight that is greater than mid section 23 and butt section 24 weight.

In practice and when a golfer chooses to adjust the bending profile the golfer will first remove the inner shaft structure 16 by removing hex cap 19 via a hex wrench. Once removed the inner shaft structure 16 is then disassembled and either/or tip section 22, mid section 23 or butt section 24 is replaced. The inner shaft structure 16 is then placed back within the outer shaft structure 18. The hex cap 19 is then threaded back on and tightened.

Although in the preferred embodiment three sections are shown those skilled in the art will readily recognize and appreciate that a plurality of sections can be used and in doing so will not deviate from the scope or the spirit of the present invention. Those skilled in the art would also appreciate that using a plurality of independent shaft structures would allow for a finer tuning of the overall bending profile.

FIG. 10 reveals an alternative embodiment of the inner shaft structure 16. Inner shaft structure 16 includes a single support member 84 which is used to accommodate and support spacers 72, 74, 76 and 78 as well as stiffening sleeve 82 and weights 80. Support member 84 can be chosen to achieve a certain torque rating by virtue of the diameter and material chosen. In this embodiment, a precise bending profile is achieved by the combination and placement of spacers 72, 74, 76 and 78 in combination with the placement, length and stiffness of stiffening sleeves 82. The overall target weight of shaft 12 can be tuned by the choice of weights 80. The moment-of-inertia can be tuned by the location of the weights 80.

In practice, the golfer would choose the spacers 72, 74, 76 and 78 and location to affect the position of the kick-point of the overall shaft 12. For instance, to achieve a mid kick-point spacers 72, 74 76 and 78 would be placed at the proximal end of support member 84. To further affect the bending profile a golfer would choose the number, length, stiffness and placement of any number of stiffening sleeves 82 on support member 84. After placement of both the spacers 72, 74, 76 and 78 as well as stiffening sleeve 82 a final target weight would be achieved by virtue of weights 80. A final moment-of-inertia would be achieved by placing the weights 80 along support member 84 to affect the choice of moment-of-inertia required. Support spacers 72, 74, 76 and 78 are locked in place along support member 84 by virtue of a set screw arrangement.

FIG. 11 reveals yet another embodiment of the current invention wherein the inner shaft 16 is in direct contact with the outer shaft 18 serving to eliminate the need for spacers 15, 17 and 19. The combination of the inner shaft 16 structure with the outer shaft structure 18 forms in effect a complete golf shaft 12 whose combined bending profile, wall thickness, weight and torque are identical to a typical golf shaft 12. In this manner the bending profile of the outer shaft 18 directly influences the inner shaft structure 16 since the outer surface of the inner shaft structure 16 is in direct contact with the inner surface of the outer shaft structure 18.

FIG. 12 reveals yet another embodiment of the current invention where in lieu of spacers 15, 17 and 19 a thin layer of fluid 32 is provided between outer shaft structure 18 and inner shaft structure 16 in order to mechanically convey the loading of the outer shaft structure 18 to inner shaft structure 16. Those skilled in the art will recognize that virtually any fluid or material can be used in lieu of fluid 32 and that in doing so does not deviate from the spirit or intent of the current invention.

Claims

1. A configurable shaft structure, comprising an outer shaft structure and an interchangeable inner shaft structure; said interchangeable inner shaft structure being detachably connected to said outer shaft structure.

2. The shaft structure as in claim 1, wherein said interchangeable inner shaft structure includes a characteristic of a stiffness.

3. The shaft structure as in claim 2, wherein said stiffness of said interchangeable inner shaft structure varies along the longitudinal axis of said interchangeable inner shaft structure.

4. The shaft structure as in claim 1, wherein said interchangeable inner shaft structure includes a characteristic of a weight.

5. The shaft structure as in claim 4, wherein said weight of said interchangeable inner shaft structure varies along the longitudinal axis of said interchangeable inner shaft structure.

6. The shaft structure as in claim 1, wherein said interchangeable inner shaft structure includes a characteristic of a torsional rigidity about the longitudinal axis.

7. The shaft structure as in claim 6, wherein said torsional rigidity of said interchangeable inner shaft structure varies along the longitudinal axis of said interchangeable inner shaft structure.

8. A configurable shaft structure as in claim 1, wherein said interchangeable inner shaft structure includes a male coupling device and said outer shaft section includes a female coupling device wherein said female coupling device receives said male coupling device in mechanical cooperation to mechanically convey rotational motion thereof.

9. A configurable shaft structure as in claim 8, wherein said male coupling device and said female coupling device include a locking mechanism.

10. A modifiable shaft structure, comprising an outer shaft structure and a plurality of interchangeable inner shaft structures; wherein at least one said interchangeable inner shaft structure being in mechanical cooperation with said outer shaft structure whereby the loading of said outer shaft structure transfers same said loading upon said interchangeable inner shaft structure such that the combination of resistance to said loading is generated from the reaction of said outer shaft structure and said interchangeable inner shaft structure to said loading; whereby the weight of said modifiable shaft structure is derived from the weight of said outer shaft structure and the weight of said interchangeable inner shaft structure in aggregate; whereby the distribution of weight of said modifiable shaft structure is derived from the distribution of weight of said outer shaft structure and the distribution of weight of said interchangeable inner shaft structure in aggregate; whereby the torsional rigidity about the longitudinal axis of said modifiable shaft structure is derived from the torsional rigidity of said outer shaft structure and torsional rigidity of said interchangeable inner shaft structure in aggregate; each said interchangeable inner shaft structure comprising a stiffness, weight, distribution of weight and torsional rigidity wherein the stiffness, weight, distribution of weight and torsional rigidity may vary.