Compound tools – Cutter combined with other tool or tools
Reexamination Certificate
2001-10-23
2003-03-04
Noori, Max (Department: 2855)
Compound tools
Cutter combined with other tool or tools
Reexamination Certificate
active
06526613
ABSTRACT:
FIELD OF THE INVENTION
The present invention pertains generally to a device for evaluating the stiffness of a golf shaft. More particularly, the present invention pertains to a device which uses stiffness measurements to locate the spine of a golf club shaft. The present invention is particularly, but not exclusively, useful as a device for finding the spine of a golf club shaft under static conditions and then determining the dynamic stiffness of the shaft at various angles about the shaft's axis from the spine.
BACKGROUND OF THE INVENTION
A typical golf club includes a head, a shaft and a grip. The head is attached to one end of the shaft and includes a face for contact with a golf ball. An elastomeric grip covers the other end of the shaft. Typically, the shaft is elongated and substantially cylindrical. Generally, the shaft is slightly tapered from a larger cross-section at the grip end to a smaller cross-section where the head is attached.
During the golf swing, the shaft is exposed to various forces. For example, because the face of the club head is not located on the axis of the shaft, the shaft is exposed to a torsional force when the club head impacts the ball. Moreover, a lateral or bending force is imparted to the shaft both at ball impact and during portions of the golf swing when the club head is accelerated or decelerated.
The actual amount of bend and twist experienced by the shaft during the golf swing will depend on the dimensions and construction of the shaft. Specifically, the flexibility (i.e. stiffness) of the shaft will determine the amount of bend and twist experienced by the shaft during the swing and at impact with the ball. As it happens, different golfers prefer shafts having different stiffnesses. For example, tour players that have an extremely fast swing speed generally prefer stiff shafts that will bend and twist very little during the swing. Because the amount of bend and twist is reduced, the head of the club is maintained at a proper alignment relative to the shaft resulting in a “square” club face at impact. On the other hand, some players, such as women and seniors, often prefer flexible shafts. These players generally have a slower swing speed, and rely on a whipping action created by the flexible shaft to increase club head speed at ball impact. In any case, all golfers generally seek a set of clubs having little or no variation in shaft flexibility from club to club within the set.
Modern shafts are made of metal such as steel or composite materials such as carbon fiber (graphite) embedded in an epoxy matrix. During manufacture of both metal and composite shafts, a spine (sometimes called a seam) is generally created in the shaft. For example, to create a steel shaft, a flat shaft blank is typically rolled onto a tapered cylindrical mandrel and the edges of the blank are butt welded together. The weld creates a spine in the shaft that extends along the length of the shaft. Similarly, in shafts made from composite materials, fibers are generally woven into either a cloth-like material or a uni-directional tape and then impregnated with resin. In one technique, several pieces of impregnated cloth-like material or uni-directional tape are successively wrapped around a tapered cylindrical mandrel and then cured to form a composite shaft. Unfortunately, even when a substantial effort is expended to line up the ends of the successive pieces of cloth, overlaps and mismatches between the ends of adjacent pieces create a spine in the composite shaft.
Of important interest for the present invention, the spine affects the stiffness of the shaft. Specifically, the spine causes the stiffness of the shaft to vary when measured at different shaft angles. Stated another way, a different force is required to bend the shaft when the spine and axis of the shaft are in the plane of the bend than when the spine of the shaft is not in the bend plane. Importantly, this variation in stiffness can be used to locate the position of the spine of a shaft when the location of the spine is not visible. For purposes of the present disclosure, a spine plane can be defined as the plane containing both the axis of the shaft and the spine of the shaft. To locate the spine in this manner, the shaft is generally positioned horizontally with one end of the shaft clamped between two flat or “v”-shaped jaws. Then, a standard weight is attached to the second end of the shaft and the deflection of the second end is measured. Next, as the shaft is slowly rotated about the longitudinal axis of the shaft, a variation in the deflection of the second end becomes apparent. Since the spine is generally the stiffest part of the shaft, the spine location can be found by rotating the shaft until the deflection of the second end is at a minimum. Unfortunately, thin and fragile shafts are often damaged when clamped between two flat or “v” shaped jaws.
For purposes of the present disclosure, the technique for locating a spine described above is considered a static analysis since the second end of the shaft is essentially motionless when the deflection is measured. Once the position of the spine is located and marked, this information can be used in club building. Specifically, each club head can be oriented on the shaft with the spine positioned at a predetermined orientation relative to the club head face to thereby create a set of clubs having a consistent spine orientation and feel from club to club.
It is to be appreciated that when a player swings a golf club, the shaft does not always experience a simple static bend. In addition to the presence of a spine discussed above, other factors such as the orientation of fibers in a composite shaft or defects present in a metal or composite shaft can cause the stiffness of the shaft to vary with shaft angle. Unfortunately, static bend tests often fail to detect these defects. To more adequately model the dynamic golf swing and detect certain shaft defects, dynamic stiffness measurements can be used as a quality control tool to discard shafts having non-optimal dynamic stiffness.
After the spine has been located using the above described static analysis, dynamic stiffness measurements can be performed. To determine the dynamic stiffness of a shaft on various bend planes running through the shaft axis, one end of the shaft must be held. Next, the second end of the shaft is deflected and released to cause the second end of the shaft to oscillate within the original spine plane. The oscillation frequency is then measured as an indication of dynamic stiffness. The procedure can be repeated at different shaft angles. For example, the second end of the shaft can be deflected and released to oscillate in a plane normal to the original spine plane, and the oscillation frequency recorded. Once the dynamic stiffness at various shaft angles has been measured, the results can be used to discard shafts having dynamic stiffness values outside a predetermined range.
In light of the above it is an object of the present invention to provide a device suitable for the purposes of accurately determining the location of a golf club shaft spine and the dynamic stiffness of the shaft at various shaft angles relative to the spine. It is another object of the present invention to provide a device capable of performing both static and dynamic stiffness measurements on a golf club shaft without removing, realigning and regripping the shaft between tests. It is yet another object of the present invention to provide a device for measuring the stiffness of a golf club shaft having an improved clamping mechanism that firmly holds one end of the shaft during testing but does not damage thin and fragile shafts. Yet another object of the present invention is to provide a golf club evaluator which is easy to use, relatively simple to manufacture, and comparatively cost effective.
SUMMARY OF THE PREFERRED EMBODIMENTS
The present invention is directed to an apparatus for evaluating a golf club shaft. Specifically, the apparatus measures the static stiffness of the golf club sh
Noori Max
Nydegger & Associates
Penley Sports, LLC
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