WO2001027244A9

WO2001027244A9 - Body member with adjustable stiffness and frequency

Info

Publication number: WO2001027244A9
Application number: PCT/US2000/028552
Authority: WO
Inventors: Laurence Hsiao-Cheng Li; Jason Tolomeo
Original assignee: Li Laurence Hsiao Cheng; Jason Tolomeo
Priority date: 1999-10-14
Filing date: 2000-10-13
Publication date: 2001-10-25
Also published as: WO2001027244A1; AU1205701A

Abstract

The body member (250) comprises two inserts (202 and 208) positioned therein. A load member (206) extends between (202 and 208). A load adjuster (203) produces a tension force in the load member (206) and an opposite compression force on body member (250). Changes in the bending stiffness and vibrational bending frequency of the body member (250), for example when used in a golf club shaft, is proportional to the axial force applied to it.

Description

BODY MEMBER WITH ADJUSTABLE STIFFNESS AND FREQUENCY

FIELD OF THE INVENTION

This invention relates to the field of athletic equipment and, more specifically, to body members having an adjustable stiffness and frequency.

BACKGROUND

The trend in the golf club industry is towards the construction of customized golf clubs. In customizing a golf club, the physical size of the club should correspond in some way to the size of the golfer. For example, a longer golf club would be suitable for a taller golfer. The weight of the club should also be considered since, in general, a golfer with greater physical strength can swing heavier clubs than golfers of lesser strength. These are examples of two factors commonly considered when selecting the proper golf club for a particular individual. Another important parameter to consider is the bending characteristic of the golf club shaft.

The bending of a golf club shaft may be characterized by its bending stiffness and its vibrational bending frequency. The bending stiffness is a measure of how much the golf club shaft will bend (i.e., its displacement) due to an applied force at a specified location on the shaft. If the same force is applied in the same way to two different golf club shafts, the shaft with the smaller displacement is considered to be stiffer, as illustrated in Figure 1 A. The vibrational bending frequency of a golf club shaft is the frequency at which the golf club shaft vibrates when bent and then suddenly released, for example, when being held at the grip end and deflected at the head. Such vibration of the shaft is similar to the motion of a car radio antenna when struck. As the shaft vibrates, the number of times the end of the shaft goes back and forth each minute is the vibrational bending frequency measured in cycles per minute. It is common for golf clubs to be purchased pre-assembled as a set, with the golfer required to adapt to the golf clubs as purchased. Some golf clubs may be selected off- the-shelf with a particular stiffness specification that the golfer deems appropriate for his or her golfing style. Golf club shafts are currently commercially sold in different bending stiffness specifications, examples are: "ladies," "regular," "stiff," and "extra stiff." Each of these specifications relates to a range of bending stiffness values. The exact value of an individual shaft designated with one of the above terms falls somewhere within the range of values described by that specification. The purpose of these various shaft bending stiffnesses is to allow the custom assembly of a golf club with a vibrational bending frequency that best compliments a golfer's particular strength and swing speed. One problem with selecting golf clubs with a fixed bending stiffness and vibrational bending frequency is that it is rare for a golfer's swing tempo to precisely match with an off-the-shelf set of clubs. Another problem is that it is also rare for a set of clubs to have physical parameters such as bending stiffness, mass, and vibrational bending frequency consistent between each club within a set.

One solution is to provide a custom made set of clubs where a golf professional or person with technical expertise consults with the golfer prior to the assembly of the golf club. The consultant chooses the golf club shaft bending stiffness, length, and head weight to best suit the individual golfer. A problem with providing a custom set of clubs is that commonly only a range of discrete vibrational bending frequencies are attainable. Furthermore, the range of discrete vibrational bending frequencies may not be available at all for certain combinations of shaft length and head weight. In addition, once the club is assembled the vibrational bending frequency and shaft bending stiffness cannot easily be changed without re- manufacturing the golf club. WO 01/27244 PCTVUSOO/28552

Some prior golf club shafts are designed to provide very specific shaft bending stiffnesses at different locations along the shaft's length. One prior golf club shaft uses an interior bar, within a hollow shaft, and a number of coupling inserts to alter shaft stiffness. When engaged, the coupling inserts attach the shaft to the interior bar, thus increasing the overall stiffness of the club. A problem with such a shaft is that it may provide only minimal stiffness increase due to the inefficient location of the central bar and its contribution to the overall bending moment of inertia. Further, the mass increase of such a device on the overall club mass may be substantial in relation to the stiffness change provided. Such added weight may not be desirable with certain golfers. Another problem with some prior golf clubs shafts is that their stiffness may not be altered after they have been assembled by the manufacturer. A golfer's skill level and preferences may change over time and, thereby, the golfer may desire a different stiffness to his clubs. As such, the golfer may be compelled to purchase a new set of clubs or to disassemble and reassemble his/her clubs using new components. One prior golf club design provides the capability of changing the shaft stiffness of a golf club after it has been assembled. The golf club's stiffness may be changed by pressurizing the shaft with air. One drawback of such a device is that the use of pressure levels necessary to achieve a real benefit may create significant safety issues.

As such, these prior golf clubs do not provide the individual golfer with the capability of changing the bending stiffness and the vibrational bending frequency of a given set of clubs after the clubs have been assembled and purchased without substantially changing the mass of the club or introducing significant safety issues.

SUMMARY OF THE INVENTION The present invention pertains to an apparatus for force adjustment within a body member. The apparatus includes a body member and a load member disposed within the body member to generate a force on the body member. The apparatus may also include an adjuster coupled to the load member to adjust the force on the body member.

Additional features and advantages of the present invention will be apparent from the accompanying drawings and from the detailed description that follows.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is illustrated by way of example, and not by way of limitation, in the figures of the accompanying drawings and in which: Figure 1 A illustrates the principles of bending stiffness.

Figure IB illustrates one embodiment of a golf club having a force tuning device. Figure 2 illustrates a cut through view of one embodiment of a body member.

Figure 3 illustrates one embodiment of the internal forces within a body member. Figure 4 illustrates one embodiment of an adjuster for adjusting the bending stiffness and vibrational bending frequency of a body member.

Figure 5 A illustrates a cross section of one embodiment of a body member. Figure 5B illustrates cross sections of alternative embodiments of a coupler.

Figure 5C illustrates alternative embodiments of a screw mechanism. Figure 6 illustrates an exploded view of one embodiment of a force tuning device contained within a body member.

Figure 7 illustrates an alternative embodiment of insert assembly in a body member.

DETAILED DESCRIPTION

In the following description, numerous specific details are set forth such as examples of specific materials, mechanisms, dimensions, etc. in order to provide a thorough understanding of the present invention. It will be apparent, however, to one skilled in the art that these specific details need not be employed to practice the present invention. In other instances, well known materials or methods have not been described in detail in order to avoid unnecessarily obscuring the present invention.

An apparatus for force tuning within a body member is described herein. In one embodiment, the apparatus includes a body member having a bending stiffness and a vibrational bending frequency. A load member is coupled to the body member. The load member allows for the bending stiffness and the vibrational bending frequency to be altered. Such alteration may occur after the apparatus is assembled.

The method and apparatus described herein may be implemented with various types of devices, for example, a golf club, as discussed in detail below. The method and apparatus are described in relation to a golf club, however, only for illustrative purposes and is not meant to be limited only to use in a golf club. The apparatus described herein may also be used with other hand held devices, such as, but not limited to, a fishing rod and a tennis racket.

Figure IB illustrates one embodiment of a golf club having a force tuning device. Golf club 10 includes a head 20 and a body member 50. When discussing golf clubs, body member 50 may be referred to as a shaft. Body member 50 has a head end 25 and a handle end 30. Head end 25 may be coupled to head 20. In one embodiment, handle end 30 is an area of body member 50 by which a user typically holds golf club 10. Handle end 30 may be wrapped in a material suitable for gripping by the user. In another embodiment, handle end 30 may be coupled to a separate handle piece. The axial direction 15 is along the length of golf club 10.

The performance of golf club 10 may be characterized by parameters such as its bending stiffness and its vibrational bending frequency. The bending stiffness of body member 50 is a measure of how much the body member will bend due to an applied force at a specified location. The vibrational bending frequency of body member 50 is the frequency at which body member 50 vibrates when bent and then suddenly released, for example, when being held at handle 30 and deflected at head 20. As body member 50 vibrates, the number of times that head end 25 moves back and forth, per a time period, is its vibrational bending frequency.

The vibrational bending frequency depends on the bending stiffness of the body member 50, as well as the mass of body member 50 and head 20. If body member 50 is made stiffer, with the mass of body member 50 and head 20 constant, the vibrational bending frequency increases. Conversely, if the mass of body member 50 or head 20 is increased, with the bending stiffness of body member 50 remaining constant, the vibrational bending frequency decreases. Thus, the vibrational bending frequency of golf club 10 may be changed by altering its mass and/or its bending stiffness. Golf club 10 includes a device, within body member 50, for adjusting a force on body member 50 that is proportional to the change in bending stiffness and vibrational bending frequency of golf club 10.

Figure 2 illustrates a cut through view of one embodiment of a body member. In one embodiment, for example, body member 250 may be body member 50 of Figure 1, with section A-A of Figure 2 corresponding to section A- A of Figure IB.

In one embodiment, body member 250 has a circular cross sectional structure with a cavity to contain a mechanism for adjusting the stiffness and frequency of the body member. In alternative embodiments, body member 250 may have another cross sectional structure, for example, a square shape or an oval shape.

In one embodiment, body member 250 includes inner insert 208 and outer insert 202. The size and diameter of inserts 202 and 208 may be designed to provide coupling within body member 250 at a desired location. Inserts 202 and 208 are positioned within body member 250 around the section where stiffness of the body member is to be adjusted, as discussed below. In one embodiment, outer insert 202 may be coupled to body member 250 at one of its ends and inner insert 208 may be coupled to body member 250 at its approximate center. In an alternative embodiment, an insert may be coupled at other positions within body member 250, for example, at the other end of body member 250.

In one embodiment, inserts 202 and 208 may be coupled to body member 250 through bonding. In an alternative embodiment, inserts 202 and 208 may be constrained within body member 250 by other methods, for example, integrally manufactured into body member 250. Such methods are well known in the art; accordingly, a more detailed description is not provided herein.

A load member 206 extends between inserts 202 and 208. Load member 206 may be coupled to inner insert 208 at one end. The other end of load member 206 may be coupled to outer insert 202. In one embodiment, load member 206 carries a tension load between the inserts 202 and 208 so that the section of body member 250 between inserts 202 and 208 may be subjected to compression along axial direction 215.

In one embodiment, load member 206 is a rod. In alternative embodiments, load member 206 may be another type of elongated structural member capable of carrying a tension force along axial direction 215 of body member 250, for example, a tube or a cable. Load member 206 may be constructed of a tension retaining material that does not exhibit significant time degradation or creep that would lessen the amount of force carried. Creep refers to the property of a material whereby the physical dimension of the loaded part changes as a function of time as well as load. Steel, aluminum, titanium, invar, carbon fiber composites and boron fiber composites are examples of such materials that are highly resistant to creep. In an alternative embodiment, load member 206 may be configured to carry a compressive load.

The inserts and the load member are not limited only to the configuration illustrated in Figure 2. As previously discussed, in an alternative embodiment, the inserts 202 and 208 may be located along different locations of body member 50 of Figure 2 in order to target the stiffness along prescribed regions of its length. For example, insert 208 may be located at the head end 25 of Figure 1 to provide a greater effect on the kick- point of golf club 10 of Figure 1. The kick-point of a golf club is the location on the golf shaft at which the shaft exhibits the most curvature for a given deflection. In alternative embodiments, where the golf club has a multiple piece shaft, the inserts and load member may be built into one or more of the shaft pieces.

Referring again to Figure 2, in one embodiment, a load adjuster 203 is coupled to load member 206. Tuning of the bending stiffness and vibrational bending frequency of body member 250 may be performed at any time through use of load adjuster 203. In one embodiment, the tuning may be performed by turning load adjuster 203 in a rotational direction 216. Rotating load adjuster 203 produces a tension force in load member 206 and an opposite compression force body member 250, as illustrated in Figure 3.

Figure 3 illustrates one embodiment of the internal forces within a body member. Changes in the bending stiffness and vibrational bending frequency of body member 350 is proportional to the axial force applied to it. A force 348, that is a compression load, in body member 350 causes a decrease in its bending stiffness and a corresponding decrease in its vibrational bending frequency. Conversely, if force 349 on load member 306 is a tension load, reduction of force 349, which corresponds to an equal reduction in force 348, results in an increase in the bending stiffness and vibrational bending frequency of body member 350, up to the properties of a body member without tensioning member 306. As such, a user may reversibly and repeatably tune body member 350 to a desired frequency by moving load adjuster 303.

The internal force 349 on the load member 306 is described as being a tension load and the internal force 348 on body member 350 as being a compressive load. The description would also be applicable if the internal force 349 on the load member 306 were described as a compressive load and the corresponding internal force 348 on the body member 350 as being a tension load. In this embodiment, the change in bending stiffness and vibrational bending frequency of the body member 350 increases as the compressive internal force in the load member 306 was increased. As such, the force on the load members in the figures (e.g., load 206 of Figure 2 and 406 of Figure 4) may be described as a tension load and the force on the body members of the figures (e.g., body member 250 of Figure 2 and 450 of Figure 4) may be described as a compression load for illustrative purpose only. In an alternative embodiment, the force on the load members in the figures may be a compression load and the force on the body members in the figures may be a tension load. Referring to Figure 3, if body member 350 is a golf club shaft, for example, a golfer may quickly tune the golf club to a preferred setting by turning load adjuster 303 to try the golf club at various vibrational bending frequencies. In another embodiment, the vibrational bending frequency of a golf club having body member 350 may be measured quantitatively and correlated to a calibration scale on the body member. This provides an indicator by which a golfer can visually adjust the parameters of the shaft to a given setting.

Figure 4 illustrates one embodiment of an adjuster for a force tuning device. In one embodiment, outer insert 402 is disposed within end 430 of body member 450. One end of insert 402 has a lip 413 that transitions to a larger diameter than body member 450. The edge of lip 413 seats insert 402 against body member 450 when installed and prevents insert 402 from dropping into the cavity of body member 450. As such, insert 402 provides a firm attachment point to body 450 for additional components.

In one embodiment, load member 406 is attached to a coupler 404 that may be placed to insert 402. Load adjuster 403 is attached to coupler 404 from a side opposite that of load member 406. Load member 406 extends between insert 402 and another insert (not shown) within body member 450. Load member 406 carries a tension load so that the section of body member 450 between the inserts places that section into axial compression.

In one embodiment, coupler 404 has a coupler key 407 that fits into keyway slot 412. Keyway slot 412 allows coupler 404 and load member 406 to move along the axial direction 415 of body member 450, within insert 402. Keyway slot 412 also prevents relative rotation between coupler 404 and insert 402 about the axial direction 415 of body member 450.

Figure 5 A illustrates a cross section of one embodiment of a body member. Load member 506 is attached to coupler 504 that is inserted into insert 502. In one embodiment, coupler 504 has a non-circular cross section such that a pin 507 resides at one point along its circumference. Insert 502 has a correspondingly sized keyway 512 disposed within it that will accept pin 507. Keyway 512 prevents the rotation of coupler 504 when the load adjuster (e.g., load adjuster 403 of Figure 4) is turned. This forces coupler 504 to slide up and down within insert 502 (i.e., into and out of the page) in response to the amount of tension being applied by the load adjuster (not shown). In another embodiment, coupler 504 may be formed as an integral part of load member 506. In alternative embodiments, coupler 504 may have other configurations to allow for axial motion of load member 506 (into and out of the page) while preventing rotation, for example, a spline, a flat, and a square, as illustrated in Figure 5B. Referring again to Figure 4, coupler 404 is coupled to load adjuster 403. In one embodiment, coupler 404 may be a screw mechanism. Coupler 404 may have male or female threads where it attaches to load adjuster 403. Turning load adjuster 403 in one direction causes coupler 403 to bring load member 406 and load adjuster 403 closer together. This movement produces a tension force in load member 406 and an opposite compression force in body member 450, similar to that discussed above in relation to Figure 3. Various configurations of a screw mechanism are illustrated in Figure 5C. For example, the load member and coupler may be integrated into one component 505 of Figure 5C. In an alternate embodiment, coupler 404 may be another type of mechanisms for providing an axial load to load member 406, for example, a cam mechanism. Screw and cam mechanisms are well known in the art; accordingly, a more detailed description of their operation is not provided herein.

As such, the tuning of the bending stiffness and the vibrational bending frequency of body member 450 may be performed by adjusting load adjuster 403. In addition, this tuning procedure may be performed at any time after the assembly of the components within body member 450. The use of a linear screw mechanism enables the bending stiffness and vibrational bending frequency to adjusted over a continuous range of values, rather than just a few discrete values. In an alternative embodiment, a non-linear mechanism may be used to provide adjustment in a discrete range of values, for example, a ratchet mechanism. In one embodiment, spring 411 may be positioned between load adjuster 403 and insert 402 to provide approximately a constant tension in body member 450, regardless of the amount of bending deflection of body member 450. In one embodiment, spring 411 may be belleville springs for compactness, as shown in Figure 4. In alternative embodiments, spring 411 may have other designs, for example, it may be a compressive or extensive coil spring. Spring 411 may be soft enough so that it would provide a relatively large ratio in the adjustment of load adjuster 403 to the force transmitted to load member 406. As such, changes in the force that produces tension on load member 406 may be easily controlled with broad tolerance on the adjustment requirements of load adjuster 403. This increases the robustness of the design. Without spring 411, very small changes in adjustment of load adjuster 403 may create very large tension forces if load member 406 is relatively stiff. In another embodiment, the selection of a sufficiently compliant load member 406 may reduce or eliminate the need for spring 411. Spring mechanisms are well known in the art; accordingly, a more detailed description of their operation is not provided herein.

A calibrated scale 416 may be used to provide a visual indication of the stiffness and frequency setting. In one embodiment, calibrated scale 416 may be etched on the inner surface of insert 402 and viewed as load adjuster 403 is adjusted. In alternative embodiments, calibrated scale 416 may be positioned at other locations to allow for a user to visually inspect the scale. For example, calibrated scale 416 may be positioned on the outside surface of body member 450, with a window slot cut in body member 450 and insert 402 such that the position of load adjuster 403 may be visible from the exterior of body member 450.

Figure 6 illustrates an exploded view of one embodiment of a stiffness and frequency tuning device within a body member. In one embodiment, insert 608, load member 606, coupler 604, insert 602, spring 611, and load adjuster 603 may be assembled independent of body member 650. The assembled components may then be slid into body member 650 having a bonding agent pre-applied in appropriate locations to bond the inserts. In one embodiment, insert 608 may be installed in the body member 650 by bonding insert 608 with a high strength adhesive such as an epoxy. In another embodiment, insert 608 may be coupled to body member 650 by other methods, for example, by integrally forming the insert into the body member.

Figure 7 illustrates an alternative embodiment of an insert assembly in a body member. Insert 708 may be a self-locking insert having gripping teeth 798 disposed around its outer surface. Self-locking insert 708 may be pressed into body member 750 until gripping teeth 798 bite into the inner surface 751 of body member 750. By using a self-locking insert, a bonding agent may not be necessary to anchor insert 708 to body member 750. In another embodiment, self-locking insert 708 may have other configurations, for example, the self-locking insert may be threaded to accept a load member, have a hole to accept a load member anchored by some other means, or be integrally attached to the load member.

The installation methods illustrated in Figures 6 and 7 may be performed on readily available body members without the need to alter the body member other than by attaching the force tuning device. This may reduce assembly time and cost.

The manufacturing process described above may be used to replace the current practice of manufacturing several different body member stiffness types and, thus, may reduce tooling and assembly costs for manufacturers. In addition, the use of an adjustable stiffness and frequency body member may reduce the inventory of wholesalers and retailers who currently have to carry several body members with different stiffness specifications to accommodate various users.

It should be noted again that the stiffness and frequency adjustment device discussed herein is not limited to use with only a golf club shaft. In an alternative embodiment, body member 250 may be, for example, a fishing rod or a tennis racket frame. The apparatus described herein provides a means for optimizing the frequency and stiffness of a single body member or a group of body members (e.g., a set of clubs or group of tennis rackets) to improve their feel and performance in relation to an individual's swing. Furthermore, when used within a set of body members, the apparatus described herein may be used to match the frequency between individual body members (e.g., club shafts and racket frames) so that the entire set may be tuned to a similar desired frequency. In addition, the stiffness and frequency tuning may be accomplished after the set of body members has been assembled, without strict regard to their initial frequency values. In the foregoing specification, the invention has been described with reference to specific exemplary embodiments thereof. It will, however, be evident that various modifications and changes may be made thereto without departing from the broader spirit and scope of the invention as set forth in the appended claims. The specification and drawings are, accordingly, to be regarded in an illustrative rather than a restrictive sense.

Claims

What is claimed is:

1. An apparatus, comprising: a generally continuous elongate body member having a cross section and a neutral axis of bending located along the centerline of the body member; a load member disposed within the body member along the neutral axis for the purpose of generating an axial force on the body member such that the cross-section is substantially uniformly loaded; and an adjuster coupled to the load member to adjust the force on the body member.

2. The apparatus of claim 1, wherein the adjuster includes means for adjusting the force on the body member over a continuous range of force values, resulting in a proportional change in bending stiffhess and vibrational bending frequency of the body member.

3. The apparatus of claim 2, wherein the adjuster is a linear adjuster.

4. The apparatus of claim 3, wherein the linear mechanism is a screw mechanism.

5. The apparatus of claim 1, further comprising a spring coupled between the adjuster and the load member, the spring to provide a reduced ratio of a motion on the adjuster with the force generated on the body member.

6. The apparatus of claim 1 , wherein the body member has an end and an intermediate section, and wherein the apparatus further comprises: a first insert coupled to the end of the body member; and a second insert coupled to the intermediate section, the load member coupled to the first and the second inserts.

7. The apparatus of claim 6, further comprising a spring coupled between the second insert and the adjuster, the spring to provide a reduced ratio of a motion of the adjuster with the force generated on the body member.

8. The apparatus of claim 7, wherein the load member is a rod.

9. The apparatus of claim 7, wherein the load member is constructed of a creep resistant material.

10. The apparatus of claim 9, wherein the load member is constructed of a material selected from the group consisting of steel, aluminum, titanium, invar, carbon fiber composite, and boron fiber composite.

11. The apparatus of claim 6, further comprising a screw coupler connected between the load member and the adjuster, the adjuster extending into the second insert.

12. The apparatus of claim 7, further comprising a scale coupled to the body member, the scale operable to indicate the force on the body member.

13. A golf club, comprising: a head; and a body member coupled to the head, the body member having an axial direction along a central axis, the body member comprising: a load member disposed within the body member to generate an axial force on the body member along the central axis to place a cross section of the body member in a condition of substantially uniform loading; and an adjuster coupled to the load member to adjust the force on the body member.

14. The golf club of claim 13, wherein the adjuster includes means for altering the force on the body member over a continuous range of values, resulting in a proportional change in a bending stiffness and a vibrational bending frequency of the golf club .

15. A method of assembling a force tuning apparatus, comprising: coupling a load member to an inner insert; coupling a load adjustable outer insert to the load member; positioning the inserts within a non-articulated body member such that the load member is aligned along a neutral bending axis of the body member; and securing the inserts to the body member.

16. The method of claim 15, further comprising tuning a force on the load member using the load adjustable insert.

17. The method of claim 15, wherein the inner insert is a self-locking insert and wherein the inner insert is secured to the body member by pressing the inner insert into the body member.

18. The method of claim 16, further comprising: coupling a scale to the body member; and calibrating the scale to correlate the scale with the tuning of the force on the load member.

19. The method of claim 16, wherein the force applied at the neutral axis on the load member is a tensile force which puts the body member into a substantially uniform compression, thereby reducing a bending stiffness of the body member.

20. The method of claim 15, wherein the body member is a hollow golf club shaft.

21. The apparatus of claim 1 , wherein the body member has a bending stiffhess along the axial direction and the force places the body member in compression to reduce the bending stiffhess of the body member.

22. The apparatus of claim 1, wherein the body member includes a handle portion located at an end thereof for allowing a user to grip and swing the apparatus in a sporting activity that utilizes a flexing of the body member.

23. The apparatus of claim of claim 22, wherein the apparatus is a golf club.

24. The golf club of claim 13, wherein the body member has a stiffness along the axial direction and the force places the body member in compression to reduce the stiffhess of the body member.