US20040142760A1

US20040142760A1 - Low torque composite golf shaft

Info

Publication number: US20040142760A1
Application number: US10/349,161
Authority: US
Inventors: Neal Haas; Donald Brown
Original assignee: Individual
Current assignee: True Temper Sports Inc
Priority date: 2003-01-22
Filing date: 2003-01-22
Publication date: 2004-07-22

Abstract

A golf shaft is provided having a tip portion and a butt portion. The shaft includes a first torsionally resistant flag extending along the entire length of the shaft. The shaft also includes a second torsionally resistant flag which only extends over the tip portion of the shaft. In this way, the tip portion of the shaft includes two torsionally resistant flags for providing enhanced torsion resistance without negatively impacting the bending stiffness or weight of the overall shaft.

Description

FIELD OF THE INVENTION

The present invention relates to golf shafts and more particularly, to a golf shaft having a low torque performance profile.

BACKGROUND OF THE INVENTION

A modern trend within the golf industry is to employ larger and larger driver heads. The theory behind this trend is that a large driver head provides a bigger sweet spot on the face within which good momentum transfer will take place between the head and a golf ball. This should translate into greater distance.

One drawback of large driver heads is that they are more difficult to control than conventional sized driver heads. As such, the user may gain greater distance but will sacrifice shot accuracy. Much of the loss in shot accuracy is attributable to the misalignment of the driver head with the ball at impact. The center of gravity of a large driver head is offset from the longitudinal axis of the shaft by a great distance. The inertia forces set up during a down swing induce twisting in the shaft which affects the alignment of the head relative to the ball at impact. This problem is exacerbated if the ball makes contact towards the toe of the head.

Club head misalignment can be influenced by controlling the torsional stiffness of the shaft. The torsional stiffness of the shaft resists the twisting of the club head during the swing and particularly when there is less than centered contact between the ball and head. Shafts having high torsional stiffness are available in the marketplace and are generally know as low torque shafts.

One disadvantage of conventional low torque shafts is that a sacrifice in bending stiffness and weight is made in order to enhance torsional stiffness. That is, torsional resistance and bending stiffness are both increased in conventional low torque shafts. Bending stiffness provides the trajectory of the ball, the feel of the club, and contributes to the distance resulting from each hit. In general, shafts with a low bending stiffness are desirable for most golf shots.

Recent studies have shown that only the tip section of the shaft provides the torsional resistance necessary to prevent club head twisting at impact. This is because contact between the club head and ball is a very brief dynamic event and only the tip section of the shaft gets loaded during this time period. The event is effectively over before the full length of the shaft is loaded.

In view of the foregoing, it would be desirable to provide a composite shaft that incorporates the benefits of a torsionally stiff tip section without increasing the bending stiffness in the tip area as usually associated with low torque graphite shafts. By not increasing the bending stiffness of the tip, a lower bend point is provided for the shaft which maintains good overall feel. The lower bend point will also promote a desirable high ball trajectory.

SUMMARY OF THE INVENTION

A golf shaft is provided having a tip portion and a butt portion. A first torsionally resistant flag extends along the entire length of the shaft. A second torsionally resistant flag only extends over the tip portion of the shaft. In this way, the tip portion includes two torsionally resistant flags for providing enhanced torsion resistance without negatively impacting the binding stiffness or weight of the overall shaft.

In one embodiment, a plurality of bend stiffening flags are provided along the length of the shaft. These flags include a plurality of parallel fibers aligned axially relative to a longitudinal axis of the shaft. A plurality of crush resistant flags are also provided along the length of the shaft. These flags include a plurality of parallel fibers aligned perpendicularly relative to the longitudinal axis of the shaft. A first torsion resistant flag is provided along the length of the shaft and a second torsion resistant flag is provided along the tip portion of the shaft. The torsion resistant flags include a plurality of fibers arranged in a matrix extending at ±45 degrees relative to the longitudinal axis of the shaft.

Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein: [0011]
FIG. 1 is a side view showing a golf club shaft with a grip and head shown in phantom; [0012]
FIG. 2 is a view of a first flag of composite material having a first plurality of parallel non-metallic fibers extending angularly from one side of the flag to another side and woven with a second plurality of parallel non-metallic fibers which also extend from the one side to the other side of the flag all carried in an uncured plastic material; [0013]
FIG. 3 is a view of a second flag of composite material having a first plurality of parallel non-metallic fibers extending angularly from one side of the flag to an opposite side and woven with a second plurality of parallel non-metallic fibers which also extend from the one side to the other side of the flag all carried in an uncured plastic material; [0014]
FIG. 4 is a view of a third flag of composite material having a plurality of parallel non-metallic fibers extending from one end to an opposite end of the flag carried in an uncured plastic material; [0015]
FIG. 5 is a view of a fourth flag of composite material having a plurality of parallel non-metallic fibers extending from one end to an opposite end of the flag carried in an uncured plastic material; [0016]
FIG. 6 is a view of a fifth flag of composite material having a plurality of parallel non-metallic fibers extending from one end to an opposite end of the flag carried in an uncured plastic material; [0017]
FIG. 7 is a view of a sixth flag of composite material having a plurality of parallel non-metallic fibers extending from one end to an opposite end of the flag carried in an uncured plastic material; [0018]
FIG. 8 is a view of a seventh flag of composite material having a plurality of parallel non-metallic fibers extending from one side to an opposite side of the flag carried in an uncured plastic material; [0019]
FIG. 9 is a view of a eighth flag of composite material having a plurality of parallel non-metallic fibers extending from one side to an opposite side of the flag carried in an uncured plastic material; [0020]
FIG. 10 is a view of a ninth flag of composite material having a plurality of parallel non-metallic fibers extending from one side to an opposite side of the flag carried in an uncured plastic material; [0021]
FIG. 11 is a side view of a steel mandrel; [0022]
FIG. 12 is a graph showing the various diameters provided along the length of the mandrel shown in FIG. 11; [0023]
FIG. 13 is a partial sectional view showing the flags of FIGS. [0024] 2-10 wrapped on the mandrel of FIG. 11;
FIG. 14 is a partial sectional view showing the assembly of FIG. 13 after heat processing; [0025]
FIG. 15 is a graph showing the various wall thicknesses provided along the length of the shaft of FIG. 14; [0026]
FIG. 16 is a graph showing the various outside diameters provided along the length of the shaft of FIG. 14; [0027]
FIG. 17 is a graph showing the torsional resistance of the shaft of the present invention as compared to a conventional low torque shaft and a low modulus shaft of the prior art; and [0028]
FIG. 18 is a graph showing the bending stiffness of the shaft of the present invention as compared to a conventional low torque shaft and a low modulus shaft of the prior art.[0029]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

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. [0030]
Referring to FIG. 1, a [0031] 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.
As shown in FIGS. [0032] 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.
As shown in FIG. 2, the [0033] 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.
In one embodiment, the [0034] flag 24 is formed from two overlapping pieces of material 24 a and 24 b that are adhered to one-another to form the unitary flag 24. The overlap of the material pieces 24 a and 24 b 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 24 a carries the first set of parallel fibers 52 while the second material piece 24 b carries the second set of parallel fibers 56. When the two pieces of material 24 a and 24 b 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.
Preferably, the off-[0035] 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).
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. [0036]
Further, as described above, the [0037] 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.
Referring to FIG. 3, the [0038] 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.
Also as with the [0039] first flag 24, the second flag 26 is formed from two overlapping pieces of material 26 a and 26 b that are adhered to one-another to form the unitary flag 26. The overlap of the material pieces 26 a and 26 b 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 26 a carries the first set of fibers 67 while the second material piece 26 b carries the second set of fibers 70. When the two pieces of material 26 a and 26 b 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.
In one embodiment, the off-[0040] 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.
Referring to FIG. 4, the [0041] 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.
Referring to FIG. 5, the [0042] 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).
Referring to FIG. 6, the [0043] 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.
Referring to FIG. 7, the [0044] 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.
Referring to FIG. 8, the [0045] 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.
Referring to FIG. 9, the [0046] 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.
Referring to FIG. 10, the [0047] 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.
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. [0048]
It is noted that the number of fibers shown in FIGS. [0049] 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.
Referring to FIGS. 11 and 12, a [0050] 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.
For a 46 inch shaft [0051] 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.
Referring to FIG. 13, in the manufacture of the shaft [0052] 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.
Next, the [0053] 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.
Advantageously, the torsional characteristics of the [0054] 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.
Upon the completion of the assembly of the flags on the [0055] 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.
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 [0056] 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.
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. [0057]
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. [0058]

Claims

What is claimed is:

1. A shaft comprising:

a plurality of layers of material, each layer of material including a plurality of fibers in a pre-selected orientation, the plurality of layers including:

a first layer of material including at least two sets of fibers arranged at an angle with respect to each other and extending along a first prescribed length of the shaft; and

a second layer of material including at least two sets of fibers arranged at an angle with respect to each other and extending along a second prescribed length of the shaft, the second prescribed length of the shaft being shorter than the first prescribed length and including a tip end of the shaft.

2. The shaft of claim 1 wherein each of said first and second layers of material further comprises:

a first set of parallel fibers aligned at about a +45 degree angle relative to the longitudinal axis of the shaft; and

a second set of parallel fibers aligned at about a −45 degree angle relative to the longitudinal axis of the shaft.

3. The shaft of claim 1 wherein the plurality of layers of material further includes:

a third layer of material including a plurality of parallel fibers aligned axially relative to a longitudinal axis of the shaft.

4. The shaft of claim 3 wherein the plurality of layers of material further includes:

a fourth layer of material including a plurality of parallel fibers aligned perpendicularly relative to the longitudinal axis of the shaft.

5. The shaft of claim 4 wherein each of said first and second layers of material further comprises:

6. A shaft comprising:

a plurality of layers of material, each layer including a plurality of fibers in a pre-selected orientation, the plurality of layers including:

at least one bend stiffening layer of material including a plurality of parallel fibers aligned along a longitudinal axis of the shaft;

at least one crush resistant layer of material including a plurality of parallel fibers aligned perpendicular to the longitudinal axis of the shaft; and

two torsion resistant layers of material, each torsion resistant layer including a first set of parallel fibers aligned at a first angle relative to the longitudinal axis of the shaft and a second set of parallel fibers aligned at a second angle relative to the longitudinal axis of the shaft and crossing the first set of parallel fibers.

7. The shaft of claim 6 wherein one of the at least two torsion resistant layers of material is located over a sub-portion of the shaft, the sub-portion including a tip section of the shaft.

8. The shaft of claim 6 wherein:

said first angle is about +45 degrees relative to the longitudinal axis of the shaft; and

said second angle is about −45 degrees relative to the longitudinal axis of the shaft.

9. A shaft comprising:

a composite material including a plurality of fibers dispersed therein in pre-selected orientations, the plurality of fibers including:

a first layer of biased fibers extending along a first prescribed length of the shaft;

a second layer of biased fibers extending along a second prescribed length of the shaft, the second prescribed length of the shaft being shorter than the first prescribed length and including a tip section of the shaft.

10. The shaft of claim 9 wherein each of said first and second layers of biased fibers further comprises:

a first set of parallel fibers aligned at about a +45 degree angle relative to a longitudinal axis of the shaft; and

11. The shaft of claim 9 wherein said plurality of fibers further includes:

a first set of parallel fibers aligned axially relative to a longitudinal axis of the shaft.

12. The shaft of claim 11 wherein the plurality of fibers further includes:

a second set of parallel fibers aligned perpendicularly relative to the longitudinal axis of the shaft.

13. A method of making a shaft comprising:

wrapping a plurality of layers of material over a mandrel, each layer of material including a plurality of fibers dispersed in an uncured plastic in a preselected orientation;

processing the uncured plastic to form a unitized structure; and

removing the mandrel;

wherein the wrapping step includes:

wrapping a first layer of material along a first prescribed length of the mandrel, the first layer of material including at least two sets of fibers arranged at an angle with respect to each other; and

wrapping a second layer of material along a second prescribed length of the mandrel, the second layer of material including at least two sets of fibers arranged at an angle with respect to each other, the second prescribed length of the mandrel being shorter than the first prescribed length and including a tip section of the mandrel.

14. The method of claim 13 wherein each of said first and second layers of material further comprises:

a first set of parallel fibers aligned at about a +45 degree angle relative to the longitudinal axis of the mandrel; and

a second set of parallel fibers aligned at about a −45 degree angle relative to the longitudinal axis of the mandrel.

15. The method of claim 13 wherein the wrapping step further includes:

wrapping a third layer of material around the mandrel, the third layer of material including a plurality of parallel fibers aligned axially relative to a longitudinal axis of the mandrel.

16. The shaft of claim 15 wherein the wrapping step further includes:

wrapping a fourth layer of material around the mandrel, the fourth layer of material including a plurality of parallel fibers aligned perpendicularly relative to the longitudinal axis of the mandrel.

17. The shaft of claim 16 wherein said first and second layers of material further comprises:

18. A method of making a shaft comprising:

wrapping at least one bend stiffening flag of material around a mandrel, the at least one bend stiffening flag of material including a plurality of parallel fibers dispersed in an uncured plastic and aligned along a longitudinal axis of the mandrel;

wrapping at least one crush resistant flag of material around the mandrel, the at least one crush resistant flag of material including a plurality of parallel fibers dispersed in an uncured plastic and aligned perpendicular to the longitudinal axis of the mandrel;

wrapping two torsion resistant flags of material around the mandrel, each of the two torsion resistant flags including a first set of parallel fibers aligned at a first angle relative to the longitudinal axis of the mandrel and a second set of parallel fibers aligned at a second angle relative to the longitudinal axis of the mandrel and crossing the first set of parallel fibers;

processing the uncured plastic to form a unitized structure; and

removing the mandrel.

19. The method of claim 18 wherein said step of wrapping two torsion resistant flags of material around the mandrel further comprises wrapping one of said two torsion resistant flags around a sub-portion of the mandrel, the sub-portion including a tip section of the mandrel.

20. The method of claim 18 wherein:

said first angle is about +45 degrees relative to the longitudinal axis of the mandrel; and

said second angle is about −45 degrees relative to the longitudinal axis of the mandrel.

21. A method of making a shaft comprising:

depositing a composite material over a mandrel, the composite material including a plurality of fibers dispersed in an uncured plastic in pre-selected orientations;

processing the uncured plastic to form a unitized structure; and

removing the mandrel;

wherein said depositing step includes:

depositing a first layer of biased fibers along a first prescribed length of the mandrel; and

depositing a second layer of biased fibers along a second prescribed length of the mandrel, the second prescribed length of the mandrel being shorter than the first prescribed length and including a tip section of the mandrel.

22. The shaft of claim 21 wherein each of said first and second layers of biased fibers further comprises:

a first set of parallel fibers aligned at about a +45 degree angle relative to a longitudinal axis of the mandrel; and

23. The method of claim 21 wherein said depositing step further includes:

depositing a first set of parallel fibers along the mandrel, the first set of parallel fibers being aligned axially relative to a longitudinal axis of the mandrel.

24. The method of claim 23 wherein said depositing step further includes:

depositing a second set of parallel fibers along the mandrel, the second set of parallel fibers being aligned perpendicularly relative to the longitudinal axis of the mandrel.