DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0030] The following description of the preferred embodiments is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses.

[0031] Referring to FIG. 1, a golf club 10 is illustrated including a shaft 12, a club head 14 shown in phantom, and a grip 16, also shown in phantom. The shaft 12, which is generally tubular with an central axial opening, includes a butt end 18 to which the grip 16 is attached and a tip end 20 to which the head 14 is secured. An intermediate section 22 of the shaft 12 extends between the butt end 18 and the tip end 20 thereof and tapers therebetween.

[0032] As shown in FIGS. 2-10, the shaft 12 is preferably formed by a plurality of flags or sheets including a first flag 24, a second flag 26, a third flag 28, a fourth flag 30, a fifth flag 32, a sixth flag 34, a seventh flag 36, an eighth flag 38, and a ninth flag 40, each of which is composed of a composite material including graphite fibers and an epoxy resin matrix which carries the fibers therein. The flags are typically cut to the desired dimensions from a larger rolls of materials.

[0033] As shown in FIG. 2, the first flag 24 includes a wide first end 42 and a narrow second end 44 axially spaced apart from the wide end 42 along an axis 46. Side 48 extends parallel to the axis 46 from the wide end 42 to the narrow end 44. Side 50 angles relative to the axis 46 from the wide end 42 to the narrow end 44. The flag 24 includes a first set of parallel graphite fibers 52 carried by an epoxy resin matrix 54 which extend at an angle with respect to the axis 46 from the side 48 to the side 50. A second set of parallel graphite fibers 56 carried by the epoxy matrix 54 extend at an angle relative to the axis 46 in a direction opposite the angular extension of the first set of fibers 52 such that the fibers 52 and 56 cross each other to form a biased ply. The off axis fibers 52 and 56 are also known in the art as cross plies and radials. Such off axis fibers provide a combination of torsional resistance and bending stiffness.

[0034] In one embodiment, the flag 24 is formed from two overlapping pieces of material 24a and 24b that are adhered to one-another to form the unitary flag 24. The overlap of the material pieces 24a and 24b is preferably offset by an amount approximately equal to a quarter wrap of the circumference of the mandrel (described below) corresponding to that portion of the flag 24. This promotes adhesion of the flag 24 to the mandrel. It should also be appreciated that the material piece 24a carries the first set of parallel fibers 52 while the second material piece 24b carries the second set of parallel fibers 56. When the two pieces of material 24a and 24b are adhered to one another to form the unitary flag 24, the fibers 52 and 56 cross the longitudinal axis 46 at opposite angles so as to cross one another and form the biased ply.

[0035] Preferably, the off-axis fibers 52 cross the axis 46 at an angle between thirty and sixty degrees and most preferably at an angle of forty-five degrees. The off-axis fibers 56 preferably cross the axis 46 at an angle between minus thirty and sixty degrees and most preferably at an angle of minus forty-five degrees. At ±45 degrees, the fibers 52 cross the fibers 56 at an angle of ninety degrees. While other crossing angles could theoretically be used, a ±45 degree orientation provides maximum torsional resistance and medium bending stiffness. That is, torsional stiffness increases along a bell curve from a minimum at a fiber alignment of 0 degrees relative to the longitudinal axis of the shaft to a maximum at a fiber alignment of 45 degrees relative to the longitudinal axis. The torsional stiffness decreases along the bell curve from the maximum at a fiber alignment of 45 degrees to a minimum at a fiber alignment of 90 degrees (relative to the longitudinal axis).

[0036] In contrast, bending stiffness linearly decreases from a maximum at a fiber alignment relative to the longitudinal axis of 0 degrees to a minimum at a fiber alignment relative to the longitudinal axis of 90 degrees. A fiber alignment of 45 degrees provides half the bending stiffness of fibers aligned at 0 degrees and twice the bending stiffness of fibers aligned at 90 degrees. For the purpose of this disclosure, flags including off-axis fibers are referred to as torsion resistant flags, flags including fibers aligned at 0 degrees are referred to as bend stiffening flags, and flags including fibers aligned at 90 degrees are referred to as crush resistant flags.

[0037] Further, as described above, the fibers 52 are preferably overlapped with the fibers 56. Alternatively, the fibers 52 and 56 could be woven in an interleaved fashion rather than being overlapped without departing from the spirit and scope of the invention. In a preferred embodiment of the present invention, when it is desirable to provide a shaft 12 (FIG. 1) having an overall length of 46 inches, the torsion resistant flag 24 includes a 15 inch long side 48, a 2.5 inch long first end 42, and a 0.35 inch long second end 44.

[0038] Referring to FIG. 3, the second flag 26 includes a first end 58 and a parallel second end 60 axially spaced apart from the first end 58 along an axis 62. Sides 64 and 66 extend parallel to one another and the axis 62 between the first end 58 and the second end 60. As with the first flag 24, the second flag 26 includes a first set of graphite fibers 67 carried by an epoxy resin matrix 68 which extend at an angle with respect to the axis 62 from the side 64 to the side 66. A second set of graphite fibers 70 carried by the epoxy matrix 68 extend at an angle relative to the axis 62 in a direction opposite the angular extension of the first set of fibers 67 such that the fibers 67 and 70 cross each other to form a biased ply.

[0039] Also as with the first flag 24, the second flag 26 is formed from two overlapping pieces of material 26a and 26b that are adhered to one-another to form the unitary flag 26. The overlap of the material pieces 26a and 26b is preferably offset by an amount approximately equal to a quarter wrap of the circumference of the mandrel (described below) corresponding to that portion of the flag 26. The material piece 26a carries the first set of fibers 67 while the second material piece 26b carries the second set of fibers 70. When the two pieces of material 26a and 26b are adhered to one another to form the unitary flag 26, the fibers 67 and 70 cross the longitudinal axis 62 at opposite angles so as to cross one another and form the biased ply.

[0040] In one embodiment, the off-axis fibers 67 cross the axis 62 at an angle of forty-five degrees while the off-axis fibers 70 cross the axis 62 at an angle of minus forty-five degrees such that the fibers 67 cross the fibers 70 at an angle of ninety degrees. Other angles such as described with reference to the first flag 24 may also be used. Also, an overlapping construction of the fibers 67 and 70 is preferred although a woven construction could also be used. When it is desirable to provide a shaft 12 (FIG. 1) having an overall length of 46 inches, the torsion resistant flag 26 includes 47 inch long sides 64 and 66 and 2.7 inch long ends 58 and 60.

[0041] Referring to FIG. 4, the third flag 28 includes a wide first end 72 and a tip or vertex 74 axially spaced apart from the wide end 72 along an axis 76. Side 78 extends parallel to the axis 76 from the wide end 72 to the vertex 74. Side 80 angles relative to the axis 76 from the wide end 72 to the vertex 74. The flag 28 includes a plurality of spaced parallel graphite fibers 82 carried by an epoxy resin matrix 84 which extend parallel with respect to the axis 76 from the wide end 72 to the vertex 74. Fibers formed in this 0 degree direction provide maximum bending stiffness for the shaft 12 (FIG. 1). For a 46 inch shaft 12 (FIG. 1), the bend stiffening flag 28 includes a 15 inch long side 78 and a 2 inch long end 72.

[0042] Referring to FIG. 5, the fourth flag 30 includes a narrow first end 86 and a wide second end 88 axially spaced apart from the narrow end 86 along an axis 90. Side 92 extends parallel to the axis 90 from the narrow end 86 to the wide end 88. Side 94 angles relative to the axis 90 from the narrow end 86 to the wide end 88. The direction of the angle of the side 94 is opposite to that of the first and third flags 24 and 28. The flag 30 includes a plurality of spaced parallel graphite fibers 96 carried by an epoxy resin matrix 98 which extend parallel with respect to the axis 90 from the narrow end 86 to the wide end 88. For a 46 inch shaft 12 (FIG. 1), the bend stiffening flag 30 includes a 47 inch long side 92, a 2.3 inch long narrow end 86, and a 4.4 inch long wide end 88. The flag 30 is then trimmed along the dot and dash line 99 shown in FIG. 5 from the wide end 88 such that the wide end 88 is 3.7 inches long and the side 94 includes a first portion 100 parallel to the axis 90 and a second portion 102 angled relative to the axis 90. This ensures rotational consistency and ply-balancing when the flag is ultimately wrapped around a mandrel (described below).

[0043] Referring to FIG. 6, the fifth flag 32 includes a narrow first end 104 and a wide second end 106 axially spaced apart from the narrow end 104 along an axis 108. Side 110 extends parallel to the axis 108 from the narrow end 104 to the wide end 106. Side 112 angles relative to the axis 108 from the narrow end 104 to the wide end 106. The side 112 angles in the same direction as the side 94 of the fourth flag 30 (FIG. 5.) The flag 32 includes a plurality of spaced parallel graphite fibers 114 carried by an epoxy resin matrix 116 which extend parallel with respect to the axis 108 from the narrow end 104 to the wide end 106. For a 46 inch shaft 12 (FIG. 1), the bend stiffening flag 32 includes a 47 inch long side 110, a 1.2 inch long narrow end 104, and a 2.3 inch long wide end 106. The flag 32 is then trimmed along the dot and dash line 117 shown in FIG. 6 from the wide end 106 such that the wide end 106 is 1.9 inches long and the side 112 includes a first portion 118 parallel to the axis 108 and a second portion 120 angled relative to the axis 108.

[0044] Referring to FIG. 7, the sixth flag 34 includes a wide first end 122 and a tip or vertex 124 axially spaced apart from the wide end 122 along an axis 126. Side 128 extends parallel to the axis 126 from the wide end 122 to the vertex 124. Side 130 angles relative to the axis 126 from the wide end 122 to the vertex 124. The flag 34 includes a plurality of spaced parallel graphite fibers 132 carried by an epoxy resin matrix 134 which extend parallel with respect to the axis 126 from the wide end 122 to the vertex 124. For a 46 inch shaft 12 (FIG. 1), the bend stiffening flag 34 includes an 8 inch long side 128 and a 2 inch long end 122.

[0045] Referring to FIG. 8, the seventh flag 36 includes a narrow first end 136 and a wide second end 138 axially spaced apart from the narrow end 136 along an axis 140. Side 142 extends parallel to the axis 140 from the narrow end 136 to the wide end 138. Side 144 angles relative to the axis 140 from the narrow end 136 to the wide end 138. The side 144 angles in the same direction as the sides 94 and 112 of the fourth and fifth flags 30 and 32 (FIGS. 5 and 6.) The flag 36 includes a plurality of spaced parallel graphite fibers 146 carried by an epoxy resin matrix 148 which extend perpendicular with respect to the axis 140 from the side 142 to the side 144. Fibers oriented in this 90 degree direction provide maximum hoop strength or crushing resistance in the resulting shaft. For a 46 inch shaft 12 (FIG. 1), the crush resistant flag 36 includes a 47 inch long side 142, a 2.3 inch long narrow end 136, and a 4.4 inch long wide end 138.

[0046] Referring to FIG. 9, the eighth flag 38 includes first and second ends 150 and 152 axially spaced apart along an axis 154. Unlike the second end 152 which is perpendicular to the axis 154, the first end 150 angles relative to the axis 154 to provide a more abrupt taper in the form of a step in the final sidewall of the shaft 12 (FIG. 12). Sides 156 and 158 are spaced apart from one another and extend parallel to the axis 154 from the first end 150 to the second end 152. The flag 38 includes a plurality of spaced parallel graphite fibers 160 carried by an epoxy resin matrix 162 which extend perpendicular with respect to the axis 154 from the side 156 to the side 158. For a 46 inch shaft 12 (FIG. 1), the crush resistant flag 38 includes a 24 inch long side 156, a 23 inch long side 158, and a 3.8 inch long second end 150.

[0047] Referring to FIG. 10, the ninth flag 40 includes a first end 164 and a parallel second end 166 axially spaced apart from the first end 164 along an axis 168. Sides 170 and 172 are spaced apart from one another and extend parallel to the axis 168 between the first end 164 and the second end 166. The flag 40 includes a plurality of spaced parallel graphite fibers 174 carried by an epoxy resin matrix 176 which extend perpendicular with respect to the axis 168 from the side 170 to the side 172. For a 46 inch shaft 12 (FIG. 1), the crush resistant flag 40 includes 0.25 inch long sides 170 and 172 and 3 inch long ends 164 and 166. The ninth flag 40 forms what is known in the art as a dog-knot which is used for pulling the shaft during the manufacturing process. This dog-knot is usually cut off to form the final shaft.

[0048] In one embodiment of the present invention, the composite material of the first—ninth flags include graphite fibers and an epoxy resin matrix. However, the fibers could be formed from fiberglass, aramid, boron or other suitable fiber materials, and the epoxy resin matrix could be polyester, vinylester, nylon, or any other suitable thermoset or thermoplastic matrix, all without departing from the spirit and scope of the invention.

[0049] It is noted that the number of fibers shown in FIGS. 2-10 is limited for illustration purposes only to show the alignment and orientation of the much larger number of fibers actually contained in each flag. As noted above, the orientation of the fibers controls the functional or style of the flag. That is, the biased or off-axis fibers (cross-plies) in FIGS. 2 and 3 provide torsion resistant flags 24 and 26. The parallel fibers aligned axially relative to the longitudinal axes in FIGS. 4-7 provide bend stiffening flags 28, 30, 32 and 34. The parallel fibers aligned perpendicularly relative to the longitudinal axes in FIGS. 8-10 provide the crush resistant flags 36, 38 and 40.

[0050] Referring to FIGS. 11 and 12, a rigid mandrel 178 having a rod-like shape and is formed from any suitable material such as, for example, steel. The mandrel 178 is formed with a small end section 180 and a large end section 182 opposite the small end section 180 along an axis 184. The mandrel 178 also includes first divergent section 186 extending from the small end 180 to a second divergent section 188. The second divergent section 188 extends to a third divergent section 190 which extends to a fourth divergent section 192. The fourth divergent section 192 extends to a fifth divergent section 194 which terminates at the large end 182. The mandrel illustrated in FIG. 11 includes exaggerated divergences for ease of viewing.

[0051] For a 46 inch shaft 12 (FIG. 1), the first divergent section 186 preferably has a length of 10 inches with a diameter at the small end 180 of 0.135 inch and a diameter at an opposite end of 0.217 inch. The second divergent section 188 preferably has a length of 8.7 inches, a diameter at the end of the first divergent section 186 of 0.217 inch and a diameter at an opposite end of 0.41 inch. The third divergent section 190 preferably has a length of 14.5 inches, a diameter at the end of the second divergent section 188 of 0.41 inch and a diameter at an opposite end of 0.531 inch. The fourth divergent section 192 preferably has a length of 8.8 inches, a diameter at the end of the third divergent section 190 of 0.531 inch and a diameter at an opposite end of 0.537 inch. The fifth divergent section 194 preferably has a length of 14 inches, a diameter at the end of the fourth divergent section 192 of 0.537 inch and a diameter at the large end 182 of 0.54 inch.

[0052] Referring to FIG. 13, in the manufacture of the shaft 12 (FIG. 1), the first—ninth flags are consecutively wrapped over the mandrel 178. In this illustration, the diameter to length ratio of the mandrel 178 is grossly exaggerated to enable the various flags wrapped thereabout to be more easily recognized. During manufacture, the first flag 24 is initially wrapped over a first axial end of the mandrel 178 known as the tip section. The angled side 50 shown in FIG. 2 causes to flag 24 to taper along the length of the mandrel 178. The angled sides or ends of other flags provide the same result.

[0053] Next, the second flag 26 is wrapped over the first flag 24 and the remainder of the mandrel 178. Thereafter, the third flag 28 is wrapped over the second flag 26 adjacent the tip end of the mandrel 178. Next, the fourth flag 30 is wrapped over the third flag 28 and second flag 26 along the length of the mandrel 178. Thereafter and in consecutive steps: the fifth flag 32 is wrapped over the fourth flag 30; the sixth flag 34 is wrapped over the fifth flag 32 adjacent the tip end of the mandrel 178; the seventh flag 36 is wrapped over the sixth flag 34 and the fifth flag 32 along the length of the mandrel 178; and the eighth flag 38 is wrapped over the seventh flag 36 proximate the butt end of the mandrel 178. Finally, the ninth flag 40 is wrapped over the eighth flag 38 adjacent the butt end of the shaft.

[0054] Advantageously, the torsional characteristics of the shaft 12 are not only dictated by the torsion resistant second flag 26, but also by the torsion resistant first flag 24. In this regard, since the first flag 24 is only wrapped around the mandrel 178 in a location that will eventually form the tip section of the shaft, the first flag 24 only effects the torsional characteristics of the tip end of the shaft. As such, the torsional resistance of the shaft 12 is specifically tailored within the tip section, where it is needed the most, to provide the desired effect during the down-swing and at club head/ball impact. Moreover, the first flag 24 does not negatively impact the bending stiffness of the shaft but rather improves the bending stiffness of the shaft, particularly in the tip section.

[0055] Upon the completion of the assembly of the flags on the mandrel 178 as described above, a heat shrinkable film (not shown) is wrapped around the sub-assembly 196 so that all portions of the flags are confined between the mandrel 178 and the heat-shrinkable film. The film-wrapped sub-assembly 196 is then processed through a heated environment where the epoxy resin matrices of the flags liquefy and generally blend together as a homogeneous mass. During this process, the film shrinks to generally define the exterior shape of the shaft. The film-wrapped sub-assembly 196 is then removed from the heated environment and is cooled to cure the homogenized epoxy resin. The result is the cured mass of plastic material 198 shown in FIG. 14 defined by the mandrel 178 and film. The film and mandrel are then removed to reveal the shaft 12 (FIG. 1) generally in the configuration shown in FIG. 14. A size-grinding process and a surface finishing process may then be performed to provide the shaft with the desired shape, parameters, and surface finish. The preferred wall thicknesses of the shaft are shown in FIG. 15 and the preferred outside diameters of the shaft are shown in FIG. 16.

[0056] As compared to shafts of the prior art, the shaft of the present invention provides enhanced torsional resistance at the tip. Advantageously, the shaft of the present invention does this without degrading the bending stiffness of the shaft. For example, FIG. 17 shows a torsional resistance comparison of the shaft of the present invention (line 200) with a conventional low torque shaft (line 202) and a standard modulus shaft (line 204). As can be seen, the new shaft provides about a 40% increase in torsional resistance at the tip end of the shaft as compared with prior art low torque shafts. Moreover, as shown in FIG. 18 where the bending stiffness of the new shaft (line 206) is compared with a conventional low torque shaft (line 208) and a standard modulus shaft (line 210), the new shaft increases torsional resistance in the tip without sacrificing bending stiffness. In fact, the new shaft provides a 20% improvement in bending stiffness at the tip end of the shaft as compared to prior art low torque shafts.

[0057] It can be appreciated from the forgoing that the shaft of the present invention has characteristics which make it very suitable for today's new generation of oversized driver heads. The high torsional stiffness of the tip promotes correct alignment of the head through impact to maximize shot accuracy. Maintaining a low bending stiffness in the tip provides a smooth, solid feel and a desirable ball trajectory. Advantageously, these characteristics are achieved at an ultralight weight which helps the golfer swing the club faster to achieve more distance.

[0058] The description of the invention is merely exemplary in nature and, thus, variations that do not depart from the gist of the invention are intended to be within the scope of the invention. Such variations are not to be regarded as a departure from the spirit and scope of the invention.