2. Background Art As millions of golfers worldwide can attest, it is difficult to meld the separate motions comprising a full range of motion swing so as to achieve impact with the clubface generally square to the ball while the clubhead is moving at a high rate of speed. The present invention provides an increase in clubhead speed by flexing the shaft to impart potential energy additional to that accumulated during the backswing, which is converted into extra clubhead kinetic energy just prior to and at impact.

Golf clubs having shafts with modifiable flexure are disclosed in the related art. U. S.

Patent No. 2,992,828 to W. A. Stewart discloses a club having a hollow shaft which is prestressed so as to remain relatively straight during the backswing and downswing, compared to a conventional shaft. In one mode a wire inside the shaft and adjacent to the leading edge is maintained under tension between plugs at the top and bottom ends of the shaft. The upper plug receives a bolt which when rotated causes the plug to act as a nut and travel upwardly on the bolt, increasing tension in the wire and thereby compressing the shaft leading edge. Tightening the wire tends to bow the shaft in a direction opposite to the direction the shaft would normally bend on the downswing. The wire is not tensioned sufficiently to bow the shaft but just enough to prestress the shaft or apply a bending stress in a direction opposite to the bending stress applied to the shaft during the downswing. In another mode an elongated column member extending the length of the shaft between upper and lower plugs has its trailing edge compressed by screwing a bolt down through the upper plug. This puts tension on the trailing side of the shaft, creating a bending stress in the shaft opposite to the downswing bending stress.

U. S. Patent No. 4,685,682 to J. T. Isabell discloses a golf club connected to a mechanism which increases or decreases shaft flexibility by varying the tension in a wire extending between the handle and clubhead. The wire is offset from the shaft by a bridge

which maximizes the effect of small changes in wire tension provided by movement of a threaded connection between the wire and clubhead. Increasing the tension in the mechanism decreases shaft flexibility; decreasing the tension increases flexibility. The device is used to determine the degree of shaft flexibility which maximizes an individual golfer's clubhead speed at impact, so that a set of clubs can be made that have the same flex characteristics.

U. S. Patent No. 5,865,688 to S. W. Bae discloses a golf club having three flex points along its shaft. At each point, the shaft diameter expands to permit the shaft to flex at that point. When the club is swung, the shaft flexes from a high flex point (i. e., a location proximate to the handle) to a mid flex point to a low flex point (i. e., a location proximate to the clubhead).

U. S. Patent No. 5,931,744 to L. E. Hackman discloses a method for reducing the stiffness of a hollow golf club shaft divided into three segments with each pair of segments connected by cone-shaped bands. The stiffness is changed by slicing or abrading the inner surface of the sidewall which typically is made from a flexible matrix material such as an epoxy in which elongated, high strength graphite fibers are embedded. Most of the fibers are arranged longitudinally to provide strength and stiffness to resist bending of the shaft.

Severing or removing selected fibers reduces the longitudinal stiffness.

3. Disclosure of Invention In one aspect the present invention provides a golf club including a handle with a cavity having an upper portion and a lower portion, a hollow shaft upper portion terminating in an upper end closely received within the cavity lower portion and symmetric about a longitudinal axis, a hollow flexible shaft central portion symmetric about the axis and attached at an upper end to the shaft upper portion and attached at a lower end to a hollow shaft lower portion symmetric about the axis, with the shaft lower portion terminating in a lower end. The club further includes a metallic wire having opposed upper and lower wire- ends with the upper wire-end attached to an upper wire-end retainer assembly disposed within the cavity and the lower wire-end attached to a lower wire-end retainer assembly attached to the lower end of the shaft lower portion. The wire is disposed along the longitudinal axis and is under tension.

In another aspect the invention provides a golf club including a handle with a cavity

rotatably connected to a hollow shaft upper portion symmetric about a longitudinal axis. The club further includes a hollow flexible shaft central portion attached to the shaft upper portion and a hollow shaft lower portion both symmetric about the axis. The club further includes means for altering the tension on a metallic wire disposed along the axis whose upper end is longitudinally adjustable within the handle cavity, and whose lower end is attached to the shaft lower portion at its lower end.

In still aspect the invention provides a golf club including a handle having a cap portion and a rotatable grip upper portion with a cylindrical interior surface determining a cavity. The club further includes: an upper wire-end retainer assembly including a cap- shaped outer tension tuner member having a cylindrical outer surface attached to the grip upper portion and an internal thread; a cylindrical collar having an outer surface and an internal thread which extends upwardly in a cylindrical inner tension tuner member having an external thread in threaded combination with the internal thread of the outer tension tuner member, and an internal thread ; a cylindrical outer twist-prevention housing having an upper portion with a polygonal bore and an external thread in threaded combination with the collar internal thread ; an inner twist-prevention housing having a central portion with a polygonal cross-section disposed between a cylindrical upper portion having a bore and an external thread smoothly slidable within the bore of the inner tension tuner member and a cylindrical lower portion with an external thread, with the central portion of the inner twist-prevention housing closely received within the polygonal bore; a cap-shaped clamp having an internal thread in threaded combination with the external thread of the inner twist-prevention housing, with the clamp tightening a bifurcated collet having opposed jaws received within the bore of the inner twist-prevention housing upper portion. The outer tension tuner member, cap- shaped clamp, collet, collar, inner tension tuner member, outer twist-prevention housing upper portion, and inner twist-prevention upper portion are received within the cavity, and the retainer assembly moves longitudinally within the cavity when the handle is rotated.

The club further includes: a hollow inflexible shaft upper portion, symmetric about a longitudinal axis and covered by a grip lower portion, into which the outer and inner twist- prevention housings extend; a hollow flexible shaft central portion, symmetric about the axis and attached to the shaft upper portion ; and a hollow inflexible shaft lower portion attached to the shaft central portion and symmetric about the axis.

The club further includes a lower wire-end retainer assembly including a cylindrical sleeve extending in a cylindrical flange, and a ring received within the flange. The flange is rigidly attached to the shaft lower portion at its lower end.

The club further includes a metallic wire having opposed upper and lower ends disposed along the axis. The upper end is clamped between the collet jaws, and the lower end is attached to the ring. Moving the upper wire-end longitudinally alters the tension on the wire.

In yet another aspect the invention provides a golf club including a handle with a cavity having upper and lower portions, and a hollow shaft upper portion terminating in an upper end received within the cavity lower portion and symmetric about a longitudinal axis.

The club further includes a hollow flexible shaft central portion, symmetric about the axis, which is attached at an upper end to the shaft upper portion and attached at a lower end to a hollow shaft lower portion, symmetric about the axis, which terminates in a lower end. The club further includes means for maintaining a preselected constant tension on a metallic wire, having opposed upper and lower wire-ends, which is disposed along the axis. The upper wire-end is maintained at a fixed position within the cavity upper portion, and the lower wire- end is attached to the lower end of the shaft lower portion.

In still another aspect the invention provides a golf club including a handle having a cap portion attached to a grip portion having a cylindrical interior surface and a scallop- contoured, downwardly tapering exterior surface. The cap portion and interior surface determine a cylindrical cavity having upper and lower portions. The club further includes a hollow downwardly tapering shaft upper portion terminating in an upper end received within the cavity lower portion and symmetric about a longitudinal axis, a hollow flexible, downwardly tapering shaft central portion, symmetric about the axis, which is attached at an upper end to the shaft upper portion and attached at a lower end to a hollow shaft lower portion, symmetric about the axis, having an inner wall and terminating in a lower end. The club further includes an upper wire-end retainer assembly including a cap member having a top portion, an inner thread, and a cylindrical outer surface received within the handle cavity upper portion. The retainer assembly further includes a radially compressible, hexagonal- shaped wire-end clamping member having opposed upper and lower ends, an outer surface, and a constant cross-section longitudinal bore therethrough. The cap member is superposed

upon the clamping member after it is compressed. The retainer assembly further includes a tension support member having a cylindrical lower portion received within the shaft upper portion, a cylindrical upper portion having an outer thread, and an annular flange having opposed upper and lower surfaces. The flange is disposed between and attached to the upper and lower portions, and the flange lower surface contacts the upper end of the shaft upper portion. The cap member inner thread is in threaded combination with the outer thread of the tension support member upper portion. The club further includes a lower wire-end retainer assembly including a cylindrical sleeve extending in a cylindrical flange. The sleeve and flange have therethrough a common bore, and a ring is received within the flange. The flange is attached to the inner wall of the shaft lower portion at its lower end. The club further includes a constant cross-section metallic wire having opposed upper and lower wire-ends and disposed along the longitudinal axis. The upper wire-end is closely received within the bore of the wire-end clamping member and is secured therein after the clamping member is radially compressed. The lower wire-end is attached to the ring of the lower wire-end retainer. The wire has a constant preselected tension.

A more complete understanding of the present invention will be gained from a consideration of the following description of the modes for carrying out the invention read in conjunction with the accompanying drawings provided herein. In the figures and description, numerals indicate the various features of the several modes, like numerals referring to like features throughout both the drawings and description.

4. Brief Description of Drawings FIG. 1 is a perspective view of a golf club with a hollow shaft and clubhead according to a first mode of the invention.

FIG. 2 is a longitudinal sectional view of the FIG. 1 club showing a longitudinally adjustable upper wire-end retainer assembly, a fixed lower wire-end retainer assembly, and a tension wire along the shaft longitudinal axis passing through and centered by six wire support members and clamped between the two assemblies.

FIG. 3 is a greatly enlarged sectional view taken along line 3-3 in FIG. 1 showing the FIG. 2 lower wire-end retainer assembly including a flanged sleeve and a ring, and the wire lower portion and two lowermost support members.

FIG. 4 is an exploded perspective view of the FIGs. 2,3 lower wire-end retainer assembly, and a partial sectional view of the shaft lower portion.

FIG. 5 is an exploded perspective and partial sectional view of the FIG. 1 club handle and upper wire-end retainer assembly, the assembly including a cap-shaped outer tension tuner member, a cap-shaped collet clamp, a bifurcated collet, an inner twist-prevention housing, a collar extending upwardly in an inner tension tuner member, an outer twist- prevention housing, and a stop nut.

FIG. 6 is a greatly enlarged sectional view taken along line 6-6 in FIG. 1 showing the upper wire-end retainer assembly in its lowermost position resulting in minimum wire tension.

FIG. 7 shows the same view as FIG. 6 when the upper wire-end retainer is in its uppermost position resulting in maximum wire tension.

FIG. 8 is a perspective view of the support member shown in FIGs. 2,3,4 and 6.

FIG. 9 is a perspective view of a golf club with a hollow shaft and clubhead according to second and third modes of the invention.

FIG. 10 is a longitudinal sectional view of the FIG. 9 club according to the second mode showing a fixed upper wire-end retainer assembly, a fixed lower wire-end retainer assembly, and a thin, round tension wire along the shaft longitudinal axis passing through and centered by six wire support members and clamped between the two assemblies.

FIG. 11 is a greatly enlarged sectional view taken along line 11-11 in FIG. 9 showing the FIG. 10 lower wire-end retainer assembly including a flanged sleeve and a ring, and the wire lower portion and the two lowermost support members.

FIG. 12 is an exploded perspective view of the FIGs. 10,11 lower wire-end retainer assembly, and a partial sectional view of the shaft lower portion.

FIG. 13 is a perspective view of a wire support member according to the second

mode.

FIG. 14 is an exploded perspective and partial sectional view of the FIG. 9 club handle and FIG. 10 upper wire-end retainer assembly. The assembly includes a cap member, a wire-end clamping member, and a tension support member having a cylindrical lower portion received within the shaft, an upper threaded portion, and a flange disposed between the lower and upper portions.

FIG. 15 is a greatly enlarged sectional view taken along line 15-15 in FIG. 9 showing the upper wire-end retainer assembly.

FIG. 16 is a longitudinal sectional view of the FIG. 9 club according to the third mode showing the FIGs. 10,14 fixed upper wire-end retainer assembly, the FIGs. 10,11,12 fixed lower wire-end retainer assembly, and a thin, flat tension wire along the shaft longitudinal axis passing through and centered by six wire support members and clamped between the two assemblies.

FIG. 17 is a greatly enlarged sectional view taken along line 17-17 in FIG. 9 showing the FIG. 16 lower wire-end retainer assembly including a flanged sleeve and a ring, and the wire lower portion and the two lowermost support members.

FIG. 18 is an exploded perspective view of the FIGs. 16. 17 lower wire-end retainer assembly, and a partial sectional view of the shaft lower portion.

FIG. 19 is a perspective view of a wire support member according to the third mode.

FIG. 20 is an exploded perspective and partial sectional view of the FIG. 9 club handle and FIG. 16 upper wire-end retainer assembly. The assembly includes a cap member, a wire-end clamping member, and a tension support member having a cylindrical lower portion received within the shaft, an upper threaded portion, and a flange disposed between the lower and upper portions.

FIG. 21 is a greatly enlarged sectional view taken along line 21-21 in FIG. 9 showing the upper wire-end retainer assembly.

5. Modes for Carrying Out the Invention While the present invention is open to various modifications and alternative constructions, the modes for carrying out the invention shown in the drawings are described herein in detail. It is to be understood, however, there is no intention to limit the invention to the particular modes disclosed. On the contrary, it is intended that the invention cover all modifications, equivalences and alternative constructions falling within the spirit and scope of the invention as expressed in the appended claims.

Where used herein, the word"connected"means that the two parts referred to (e. g., an external thread and a nut, or mated outer and inner threads) can be readily separated after being joined together in an interlocking combination. Where used herein, the words "attached,""attaching"and"attachment"mean that the two parts referred to are either fabricated in a single piece, or glued, clamped or crimped together. However, other forms of attachment may be suitable, consistent with simplicity of manufacture and reliability of operation.

Referring to FIGs. 1 and 2, a golf club 10 includes a rotatable handle 12 including a cap portion 13 and a grip upper portion 14 having a generally cylindrical interior surface 14A and a textured symmetrically tapering exterior surface 14B, the interior surface and cap portion determining a generally cylindrical cavity 16. Club 10 further includes a hollow inflexible, downwardly tapering shaft upper portion 18 covered by a grip lower portion 20 having a textured symmetrically tapering exterior surface 20B. a hollow flexible, downwardly tapering shaft central portion 22, a hollow clubhead 24 (not part of the invention), and a hollow inflexible shaft lower portion 26 extending into and rigidly attached at an end 26E to the clubhead. The handle and shaft upper, central and lower portions are symmetric about a common longitudinal axis. Cap portion 13 and grip portions 14 and 20 are conventionally made of a vulcanized rubber. Disposed along and within the shaft upper, central and lower portions is a plurality of wire support members 28A, 28B, 28C, 28D, 28E, 28F, progressively downwardly smaller in size, each of which is generally spherical and has therethrough a diametral bore 30 (see FIG. 8). Preferably, the number of support members is six; alternatively, five or seven members can be used. Alternatively, the members can be conical frustums sized to match the shaft's internal taper. The support members are fabricated from a low friction coefficient material such as a synthetic resinous fluorine-

containing polymer or a polyvinyl chloride (PVC) and are rigidly attached to the shaft upper, central and lower portions, preferably adhesively, so that each bore is aligned with the longitudinal axis.

Referring to FIG. 2, a tension wire 32 is clamped at opposed upper and lower ends 32U, 32L to, respectively, an upper wire-end retainer assembly 34 closely received within the cavity 16. and a lower wire-end retainer assembly 36 closely received within and rigidly attached to the shaft lower portion end 26E. As best shown in FIGs. 3 and 6, the wire 32 is threaded through each bore 30 so that the wire is constrained to be disposed along the longitudinal axis. The bores are sized to closely receive but not frictionally interfere with the wire. Preferably, the wire is made from a stainless steel having a Rockwell hardness in the range 40-70, and has a constant diameter in a range from 0.060- to 0.090-inch. Alternatively, the wire is made from a carbon steel having a Rockwell hardness in the range 40-75 with a constant diameter in a range from 0.031-to 0.064-inch. or from tungsten having a Rockwell hardness in the range 75-80 with a constant diameter in a range from 0.031-to 0.055-inch.

Referring to FIGs. 3 and 4. lower wire-end retainer assembly 36 includes a generally cylindrical sleeve 40 extending in a generally cylindrical flange 42, the sleeve and flange having therethrough a common bore 44. A generally circular ring 46 is closely received within the flange. After inserting wire-end 32L through the sleeve and into the ring and flange, the wire-end is rigidly attached to the retainer assembly by crimping the ring which, with the wire under tension, is disposed within the flange and constrained upwardly by the relatively narrow diameter sleeve. Flange 42 is rigidly attached to inner wall 26W of lower shaft portion 26 at end 26E, thereby providing additional structural integrity to the shaft- clubhead juncture.

Referring to FIGs. 5 and 6, the upper wire-end retainer assembly 34 includes a cap- shaped outer tension tuner member 50 having an internal thread 52 and an outer surface 50S, a cap-shaped collet clamp 54 having an internal thread 56, a bifuracted collet 58 having jaws 60A, 60B with generally planar inner faces 62A, 62B, respectively, and an inner twist- prevention housing 64 having a central portion 66 with a polygonal cross-section disposed between a generally cylindrical upper portion 70 with a bore 70B and an external thread 72, and a generally cylindrical lower portion 74 with an external thread 76. Wire 32 is rigidly attached to the assembly 34 when wire-end 32U is gripped between faces 62A, 62B with the

collet 58 received within the bore 70B and the clamp screwed onto member 62 by engaging threads 56 and 72. As shown in FIG. 5, handle 12 has a circumferential lower edge 12E proximate to which are ten embossed numerical indicia"0,1,2,3,4,5,6,7,8,9"evenly spaced around the circumference. Handle 12 is adhesively attached to surface 50S so that when the handle is rotated through a preselected angle the tuner member 50 also rotates through that angle. As shown in FIGs. 5,6 and 7, cap portion 13 has therethrough an air release hole 13H to allow air to escape from the hollow club 10 when the club is assembled.

Referring again to FIGs. 5 and 6, assembly 34 further includes a generally cylindrical collar 80 having an outer surface 80S adhesively attached to grip upper portion 14 and an internal thread 82. Collar 80 extends upwardly in a generally cylindrical inner tension tuner member 84 having an external thread 86 and a smooth bore 88. Assembly 34 further includes a generally cylindrical outer twist-prevention housing 90 having an upper portion 92 with a polygonal bore 94 there through and an external thread 96. Bore 94 closely receives central portion 66 of housing 64; member 50 is screwed onto member 84 by engaging threads 52 and 86; the lower portion of thread 72 is smoothly slidable within bore 88; and member upper portion 92 cooperates with collar 80 through engagement of threads 82 and 96. A stop-nut 97 is screwed onto thread 76.

Referring to FIGs. 6 and 7, when handle 12 is rotated, outer tension tuner member 50 moves through the same angle as does inner tension tuner member 84. Thread pairs (52,86) and (56, 72) are right-handed while thread pair (82,96) is left-handed, so rotating the handle clockwise causes the entire upper wire-end retainer assembly 34 to translate upwards, thereby increasing the tension on wire 32, while the wire is protected from being twisted by the interaction of housings 64 and 90. Conversely, rotating the handle counterclockwise causes assembly 34 to translate downwards, decreasing the wire tension. Preferably, the pitch of the thread pairs is such that assembly 34 moves about 1.75 mm for one complete rotation of handle 12.

Referring to FIG. 5, grip lower portion 20 terminates upwardly in a shoulder 98 on which is embossed a vertical index 98V and upper, middle and lower horizontal indices 98A, 98B. 98C, respectively. Index 98V allows precise alignment with one of the numerical indicia proximate to edge 12E so a desired shaft flexibility can be reproduced. As shown in FIGs. 6 and 7, shoulder 98 mates with a shoulder 99 in grip upper portion 14 proximate to

edge 12E. FIG. 6 shows assembly 34 when the handle is rotated fully counterclockwise so the assembly is at its extreme downward position where the shoulders mate. In this position, edge 12E touches lower index 98C. FIG. 7 shows the assembly when the handle is rotated fully clockwise so the assembly is at its extreme upward position where the shoulders 98,99 are at maximum separation. In this position, edge 12E touches upper index 98A. Stop nut 97 prevents the handle from being rotated too far.

Increasing the tension of wire 32 causes the shaft central portion 22 to flex more on the backswing than it otherwise would, storing additional potential energy as the top of the swing is reached. During the downswing this energy is converted into kinetic energy, a process analogous to releasing a bow-string to propel an arrow. This kinetic energy is imparted to the clubhead. resulting in a more powerful impact, compared to using a conventional club, as the clubhead contacts the ball.

Referring to FIGs. 9,10,14, and 15, a second mode of a golf club 100 according to the invention includes a handle 102 including a cap portion 104 and a grip portion 106 having a generally cylindrical interior surface 106A and a scallop-contoured, symmetrically downwardly tapering exterior surface 106B, the interior surface and cap portion determining a generally cylindrical cavity 108 having an upper portion 108U and a lower portion 108L.

Club 100 further includes a hollow inflexible, downwardly tapering shaft upper portion 110 which terminates in an upper end 110E closely received within cavity lower portion 108L, a hollow flexible. downwardly tapering shaft central portion 112, a hollow clubhead 114 (not part of the invention) having a generally planar clubface, and a hollow inflexible shaft lower portion 116 extending into and rigidly attached at an end 116E to the clubhead. The handle and shaft upper, central and lower portions are symmetric about a common longitudinal axis.

Cap portion 104 and grip portion 106 are conventionally made of a vulcanized rubber.

Disposed along and within the shaft upper, central and lower portions is a plurality of wire support members 118A. 118B, 118C, 118D, 118E, 118F, progressively downwardly smaller in size, each of which is generally spherical and has therethrough a diametral circular borel20 (see FIG. 13). Preferably, the number of support members is six; alternatively, five or seven members can be used. Alternatively, the members can be conical frustums sized to match the shaft's internal taper. The support members are fabricated from a low friction coefficient material such as a synthetic resinous fluorine-containing polymer or a polyvinyl chloride (PVC) and are rigidly attached to the shaft upper, central and lower portions,

preferably adhesively, with each bore aligned along the longitudinal axis.

Referring to FIG. 10, a thin tension wire 122 having a circular cross-section is attached at opposed upper and lower ends 122U, 122L to. respectively, an upper wire-end retainer assembly 124 closely received within the cavity 108. and a lower wire-end retainer assembly 126 closely received within and rigidly attached to the shaft lower portion end 116E. As best shown in FIGs. 11 and 15, wire 122 is threaded through each bore 120 so that the wire is constrained to be disposed along the longitudinal axis. Each bore is sized to closely receive but not frictionally interfere with the wire. Preferably, the wire is made from a stainless steel, titanium, or spring-wire having a Rockwell hardness in a range 30-70, and has a constant diameter in a range from 0.032- to 0.090-inch. Alternatively, the wire is made from a carbon steel having a Rockwell hardness in a range 30-75 with a constant diameter in a range from 0.025- to 0.090-inch, or from tungsten having a Rockwell hardness in the range 75-80 with a constant diameter in a range from 0.031-to 0.055-inch.

Referring to FIGs. 11 and 12, lower wire-end retainer assembly 126 includes a generally cylindrical sleeve 130 extending in a generally cylindrical flange 132, the sleeve and flange having therethrough a common bore 134. A generally circular ring 136 is closely received within the flange. After inserting wire-end 122L through the sleeve and into the ring and flange, the wire-end is rigidly attached to the retainer assembly by crimping the ring which, with the wire under tension, is disposed within the flange and constrained upwardly by the relatively narrow diameter sleeve. Flange 132 is rigidly attached to inner wall 116W of lower shaft portion 116 at end 116E, thereby providing additional structural integrity to the shaft-clubhead juncture.

Referring to FIGs. 14 and 15, the upper wire-end retainer assembly 124 includes a cap member 140 having a top portion 141 with a central inner recess 141R. an inner thread 142, and a generally cylindrical outer surface 140S, and a hexagonal-shaped wire-end clamping member 144 having opposed generally planar upper and lower ends 144U, 144L, respectively, and an outer surface 144S, and a longitudinal circular bore 146 therethrough whose diameter is initially slightly larger than the diameter of wire 122. Member 144 is fabricated from a compressible material such as stainless steel, brass, copper, titanium, tungsten, or a plastic such as a PVC. Assembly 124 further includes a tension support member 150 having a cylindrical lower portion 152 closely received within shaft upper

portion 110, a generally cylindrical upper portion 154 having an outer thread 156, and an annular flange 158 with opposed generally planar upper and lower surfaces 158U, 158L, respectively, and a generally circular perimeter surface 158S, the flange 158 attached to and disposed between lower portion 152 and upper portion 154. Portions 152,154 and flange 158 each have therethrough a circular bore 160 whose axis is along the longitudinal axis.

Preferably, member 150 is machined from a single piece of stainless steel, nickel or brass.

Alternatively, portions 152,154 and flange 158 may be fabricated separately and then adhesively attached or welded together. After first attaching wire-end 122L to retainer assembly 126, wire-end 122U is rigidly attached to assembly 124 by positioning clamping member 144 on top of upper portion 154 after tension support member lower portion 152 is inserted into shaft upper portion 110, threading wire-end 122U through bore 146 so that a tip 162 protrudes, applying a predetermined longitudinal tensile force at tip 162 to create a desired tension in the wire, and then radially compressing member 144 thereby shrinking bore 146 so that wire-end 122U is tightly secured within member 144. Cap member 140 is then connected to upper portion 154 by engaging threads 142 and 156, the tip 162 being received within recess 141R.

Because wire 122 is under tension, the shaft central portion 112 flexes more during the backswing than it otherwise would, storing additional potential energy as the top of the swing is reached. During the downswing this energy is converted into kinetic energy, a process analogous to releasing a bow-string to propel an arrow. This kinetic energy is imparted to the clubhead, resulting in a more powerful impact, compared to using a conventional club, as the clubhead contacts the ball. The amount of tension in wire 122 is selected to be in a range from about 30 pounds-weight ("pounds") to about 400 pounds.

Preferably, the wire tension in a highly flexible shaft is about 400 pounds, the tension for a shaft which is neither very flexible nor very stiff is about 175 pounds, and the tension for a shaft which has a stiff action is about 30 pounds.

Because the second and third modes of the invention are very similar, the following description of the third mode uses the same numeric indicium as in the second mode description where a third mode element is identical to a second mode element. Referring to FIGs. 9,16,20 and 21, a third mode of a golf club 200 according to the invention includes a handle 102 including a cap portion 104 and a grip portion 106 having a generally cylindrical interior surface 106A and a scallop-contoured, symmetrically downwardly tapering exterior

surface 106B, the interior surface and cap portion determining a generally cylindrical cavity 108 having an upper portion 108U and a lower portion 108L. Club 200 further includes a hollow inflexible, downwardly tapering shaft upper portion 110 which terminates in an upper end HOE closely received within cavity lower portion 108L, a hollow flexible, downwardly tapering shaft central portion 112, a hollow clubhead 114 (not part of the invention) having a generally planar clubface, and a hollow inflexible shaft lower portion 116 extending into and rigidly attached at an end 116E to the clubhead. The handle and shaft upper, central and lower portions are symmetric about a common longitudinal axis. Cap portion 104 and grip portion 106 are conventionally made of a vulcanized rubber. Disposed along and within the shaft upper, central and lower portions is a plurality of wire support members 202A, 202B, 202C. 202D, 202E. 202F, progressively downwardly smaller in size, each of which is generally spherical and has therethrough a diametral slot-shaped bore 204 (see FIG. 19).

Preferably, the number of support members is six ; alternatively, five or seven members can be used. Alternatively, the members can be conical frustums sized to match the shaft's internal taper. The support members are fabricated from a low friction coefficient material such as a synthetic resinous fluorine-containing polymer or a polyvinyl chloride (PVC) and are rigidly attached to the shaft upper, central and lower portions, preferably adhesively, with each bore aligned along the longitudinal axis and the slots aligned in a plane parallel to the plane of the clubface.

Referring to FIG. 16, a thin, flat tape-shaped tension wire 206 having a rectangular cross-section is attached at opposed upper and lower ends 206U. 206L to, respectively, an upper wire-end retainer assembly 208 closely received within the cavity 108. and a lower wire-end retainer assembly 126 closely received within and rigidly attached to the shaft lower portion end 116E. As best shown in FIGs. 17 and 21, wire 206 is threaded through each bore 204 so that the wire is constrained to be disposed along the longitudinal axis and oriented so that its width dimension is in a plane through the axis and parallel to the clubface. Each bore is sized to closely receive but not frictionally interfere with the wire. Preferably, the wire is made from a stainless steel, carbon steel, titanium, or spring-wire having a Rockwell hardness in the range 30-70, and has a constant width in a range from about 0.032- to about 0.125- inch, and a constant thickness in a range from about 0.005- to about 0.025-inch.

Alternatively, the wire is made from tungsten having a Rockwell hardness in a range 40-80, and has a constant width in a range from about 0.032- to about 0.125-inch, and a constant thickness in a range from about 0.005- to about 0.025-inch.

Referring to FIGs. 17 and 18, lower wire-end retainer assembly 126 includes a generally cylindrical sleeve 130 extending in a generally cylindrical flange 132, the sleeve and flange having therethrough a common bore 134. A generally circular ring 136 is closely received within the flange. After inserting wire-end 206L through the sleeve and into the ring and flange, the wire-end is rigidly attached to the retainer assembly by crimping the ring which, with the wire under tension, is disposed within the flange and constrained upwardly by the relatively narrow diameter sleeve. Flange 132 is rigidly attached to inner wall 116W of lower shaft portion 116 at end 116E, thereby providing additional structural integrity to the shaft-clubhead juncture.

Referring to FIGs. 20 and 21, the upper wire-end retainer assembly 208 includes a cap member 140 having a top portion 141 with a central inner recess 141R. an inner thread 142, and a generally cylindrical outer surface 140S, and a hexagonal-shaped wire-end clamping member 210 having opposed generally planar upper and lower ends 210U, 210L, respectively, and an outer surface 210S, and a longitudinal rectangular bore 212 therethrough whose cross-section dimensions are initially slightly larger than the cross-section dimensions of wire 206. Members 210 and 144 are identical except for the difference in bore shape.

Assembly 208 further includes a tension support member 150 having a cylindrical lower portion 152 closely received within shaft upper portion 110, a generally cylindrical upper portion 154 having an outer thread 156, and an annular flange 158 with opposed generally planar upper and lower surfaces 158U. 158L. respectively, and a generally circular perimeter surface 158S. the flange 158 attached to and disposed between lower portion 152 and upper portion 154. Portions 152,154 and flange 158 each have therethrough a circular bore 160 whose axis is along the longitudinal axis. After first attaching wire-end 206L to retainer assembly 126, wire-end 206U is rigidly attached to assembly 208 by positioning clamping member 210 on top of upper portion 154 and aligning bore 212 with the bores 204 after tension support member lower portion 152 is inserted into shaft upper portion 110, threading wire-end 206U through bore 212 so that a tip 214 protrudes, applying a predetermined longitudinal tensile force at tip 214 to create a desired tension in the wire, and then radially compressing member 210 thereby shrinking bore 212 so that wire-end 206U is tightly secured within member 210. Cap member 140 is then connected to upper portion 154 by engaging threads 142 and 156. the tip 214 being received within recess 141R.

The orientation of tape-shaped wire 206 in a plane parallel to the plane of the clubface enables the shaft central portion 112 to flex as in the second mode. As in the second mode, the amount of tension in wire 206 is selected to be in a range from about 30 pounds to about 400 pounds. As in the second mode, preferably, the wire tension in a highly flexible shaft is about 400 pounds, the tension for a shaft which is neither very flexible nor very stiff is about 175 pounds, and the tension for a shaft which has a stiff action is about 30 pounds.

6. Industrial Applicability None of the Background Art references addresses the problem of providing a golf club whose shaft can be made more or less flexible so that a golfer can determine by experimental trial which degree of flexibility best suits his or her particular full range of motion swing. The first mode provides a club incorporating a device which allows a player to easily increase or decrease shaft flexibility during a match or while practicing. Adjustment is calibrated so that any particular state within a range of flexibility can be accurately reproduced. The second and third modes each provide a club incorporating a device which is simpler to manufacture than the device of the first mode, resulting in a less expensive club likely to broaden market appeal. While not offering a continuous range of shaft flexibility adjustment, a buyer can select a club whose shaft has been pretensioned at the factory to that flexibility best suited to that person's swing. All three modes provide a club whose shaft imparts kinetic energy to the clubhead in the hitting zone and at impact, additional to that generated in the downswing of a conventional club.