Games using tangible projectile – Golf – Club or club support
Reexamination Certificate
1999-02-11
2003-06-24
Blau, Stephen (Department: 3711)
Games using tangible projectile
Golf
Club or club support
C473S320000
Reexamination Certificate
active
06582320
ABSTRACT:
FIELD OF INVENTION
This invention relates generally to golf clubs and, more particularly, to a hybrid shaft for improving the performance of golf clubs.
STATEMENT OF PROBLEM ADDRESSED BY INVENTION
A modern golf club typically comprises a head connected to a shaft, and a gripping region disposed on the end of the shaft opposite the head. Perhaps more than any other component, the shaft affects overall club performance. It is generally accepted that the optimum golf club shaft should have the following characteristics: (1) lightweight for high swing velocity; (2) high torsional stiffness to limit unwanted angular deflection of the head about the shaft; (3) configurable bending stiffness; (4) moderate high swing weights; and (5) energy-absorbing ability to soften shocks from miss-hits and ground strikes. These characteristics are described below in greater detail.
1. Lightweight
All golfers benefit from a lightweight club. A lightweight club will have greater acceleration for the same applied force than a heavier club. Greater acceleration equates to a higher swing velocity. Swing velocity is an important factor in driving a ball: for clubs of similar weight and mass distribution, the greater the swing velocity, the farther the ball will travel. Therefore, lighter clubs are preferable from the perspective of swing velocity.
2. High Torsional Stiffness
All golfers benefit from a torsionally-stiff shaft. The center of mass of a club head is offset from the axis of the shaft. Thus, when the club head is accelerated during the swing, inertial forces will tend to rotate the club head about the shaft axis, twisting the shaft elastically in inverse proportion to the shaft's torsional stiffness. As a result, the face of the club head does not meet the ball squarely; rather, the club head “toes” outward thereby meeting the ball at an angle. This causes the ball's flight to veer from a straight path. It is thus desirable to have the shaft as torsionally stiff as practicable to limit the adverse effects of club head rotation
The torsional stiffness of a hollow, closed section such as used for golf club shafts is proportional to both the polar moment of inertia of the section and the shear modulus of the material forming the shaft. For example, larger diameter shafts have larger polar moments of inertia and are significantly stiffer in torsion than smaller diameter sections formed from the same material. Likewise shafts formed from a material such as steel, which has a relatively high shear modulus, are inherently stiffer in torsion than a shaft with the same dimension formed from graphite which has a lower shear modulus.
3. Moderate Swing Weight
Swing weight is a measure of how the mass is distributed on a club and equates to the dynamic characteristics or “feel” of the club. Different clubs having different lengths and weights but having the same or similar swing weight will feel the same to the golfer when swung. To achieve consistent play it is important that the various clubs feel the same or at least closely similar during the swing. The swing weight parameter allows a golfer to assemble a set of clubs best suited to his particular needs by matching the dynamic characteristics (the feel) of the various clubs in the set for consistency of feel and play by matching club swing weights.
Weight concentrated toward the head of the club will tend to increase swing weight while weight concentrated toward the butt end of a club tends to decrease swing weight. Swing weight is measured on a scale for A-F, with A being the lightest swing weight and F being the heaviest. Although some golfers prefer heavy swing weights, most prefer moderate swing weights in the range of D-E.
4. Configurable Bending Stiffness
It is important to match the bending stiffness of the club to the abilities of the player. Professional golfers who are able to generate relatively high swing velocity for maximum driving distance tend to prefer clubs having a relatively high bending stiffness. On the other hand, those golfers who generate lower swing velocity tend to prefer a club with relatively low bending stiffness to take advantage of the “kick” resulting from the flexing of the shaft during the early part of the swing and the subsequent release as the golf club head squares with the ball. Thus, it is desirable to have a golf club design which affords a wide range of bending stiffness to accommodate the different needs of various players.
5. Vibration Damping
A club should absorb shock and vibration caused by the head striking the ball and/or ground. Absent such dampening, the shock is transmitted up the shaft and to the user's hands. This can be problematic, especially for those troubled with arthritis.
Conventional Golf Club Design
Conventional club shaft designs have addressed a few of the club characteristics noted above, although no one shaft design has satisfactorily addressed all of these important characteristics. The applicants are aware of essentially three conventional shaft designs: (1) a steel shaft; (2) a graphite shaft; and (3) a hybrid shaft of graphite and steel. Although these designs offer certain advantages, they tend to optimize some of the characteristics mentioned above while compromising others as described below.
1. Steel Shaft
The steel shaft has long been the mainstay of golf club design. The steel shaft provides several advantages. Steel has a high shear modulus which results in shafts having an inherently high torsional stiffness which greatly limits undesired club head rotation or toe out. A wide range of bending stiffness and swing weights can be obtained with the steel shaft by controlling the relative lengths of the smaller diameter sections of the shaft near the club head, with a more flexible shaft being provided by increasing the lengths of the more flexible, smaller diameter sections while reducing the lengths of the relatively stiffer, larger diameter sections. Steel is also durable, strong, inexpensive to manufacture, and provides great consistency of characteristics from one shaft to another.
Unfortunately, steel is dense, and clubs having steel shafts are heavy, have relatively poor acceleration and consequently a lower swing velocity. Additionally, The conventional rubber grip used with the steel shaft also contributes to the weight problem. It is a relatively heavy part of the club, representing, for example, about 15% of the total mass of a typical driver or any fairway wood. These effects are amplified for an oversized grip which are used commonly by people with arthritis or large hands.
Aside from being heavy, steel shafts also tend not to absorb or dampen vibration. Consequently, shocks tend to be transferred from the club head to the user's hands along the shaft.
Thus, although the steel shaft has some advantages, the main advantages being its wide range of bending stiffness and its high torsional stiffness, it also has serious disadvantages of being heavy and poor at absorbing or dampening shock and vibration.
2. Graphite Shaft
Clubs with composite shafts such as graphite are an improvement over steel-shafted clubs in two respects: (1) graphite is substantially less dense than steel yielding a significantly lighter shaft; and (2) a graphite shaft can absorb shock and vibration much better than a steel shaft. A lighter shaft reduces the overall weight of the club and results in higher swing velocity, which produces longer drives as explained above.
The lightweight nature of the graphite shafts are enhanced by the elimination of the rubber grip. A gripless graphite shaft does not have a separate element forming the grip, but rather, the grip is an integral part of the shaft formed by wrapping the graphite over a conically shaped mandrel having a relatively large diameter over a predetermined length at the butt end of the club. The butt end of the shaft thus has a tapered cross section and acts like the conical wedge of the conventional rubber grip to provide a comfortable and secure grip to the golfer. The shaft butt is wrapped over the length of the enlar
Blau Stephen
Synnestvedt & Lechner LLP
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