Hybrid golf club shaft

Abstract

A golf shaft for attachment to a hossel of a club head, said shaft comprising: (a) a first section comprising a first material and having a hossel end and a first joint end, said first section having a linear weight no greater than 2.4 g / in; (b) a second section comprising a second material and having a butt end and a second joint end, said second joint end being connected to said first joint end; (c) wherein said second material is less dense than said first material; and (d) wherein said first material has a shear modulus greater than that of said second material.

Description

REFERENCE TO RELATED APPLICATIONS[0001] This application is a continuation-in-part of co-pending U.S. application Ser. No. 08 / 870,625 filed on Jun. 6, 1997, which is hereby incorporated by reference, and also is based on Provisional Application No. 60 / 074,435, filed on Feb. 11, 1998, Provisional Application No. 60 / 103,375, filed on Oct. 7, 1998, and Provisional Application No. 60 / 109,707 filed on Nov. 24, 1998, all of which are hereby incorporated by reference.[0002] 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[0003] 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 ...

AI Technical Summary

Benefits of technology

[0034] The present invention provides for a golf club having a shaft of multiple sections which have a linear weight less than that of a conventional steel shaft and which are configured to contribute different properties to the club such that optimal overall club performance is achieved. In particular, high torsional stiffness and moderate swing weight are achieved synergistically by configuring the narrow section of the shaft that connects to the hossel of the head such that its linear weight is less than that of a conventional steel shaft while maintaining comparable torsional stiffness. It has been found that linear weight may be decreased while maintaining torsional stiffness by exploiting the difference between linear weight and torsional stiffness as functions of wall thickness and diameter. That is, for a given wall thickness, torsional stiffness increases more than linear weight for a given increase in diameter. Furthermore, torsional stiffness can be increased by constructing the section of a relatively-high shear modulus material such as steel. Thus, a relatively-low linear weight section with torsional stiffness comparable to that of a conventional steel shaft can be provided by increasing shaft diameter and reducing wall thickness in the proper proportions.

[0035] To reduce club weight, a majority section of the shaft comprises a lightweight material such as graphite. This section also may have a conically-shaped butt end with an enlarged diameter to provide a comfortable and secure grip for the user without the need for a conventional grip which adds considerable weight to the club. The lightweight shaft translates to greater swing velocity and commensurately further distance on a drive.

[0036] Improved vibration dampening is achieved through the use of known energy-absorbing materials in the shaft sections. A synergistic result is realized if the lightweight material used in the majority section of the shaft is also energy absorbing as is graphite. Furthermore, the use of a connector for joining the shaft to the hossel of the head has been found to be effective in dampening vibration, particularly if it is formed of an energy absorbing material like graphite. This connector also has the synergistic feature of dispersing load along a greater area of the shaft section, thereby reducing stress at the joint of the shaft and head. Vibration dampening also may be improved through the use of one or more stiffeners or plugs which are disposed in a shaft section to resist radial deformation thereto.

[0037] Variable bending stiffness is achieved by varying the relative lengths of the sections. More specifically, since the section near the hossel of the club is the most narrow part of the shaft and preferably comprises a bendable material such as steel, the relative length and diameter of this section determines the overall flexibility of the shaft. Accordingly, if a more flexible or stiffer club is desired, then the length of this section can be increased or decreased respectively. Furthermore, it has been found that the bending performance of the shaft can be adjusted through the use of one or more stiffeners as mentioned above. Thus, stiffeners have the synergistic result of not only dampening vibration but also stiffening the club, particularly if disposed in the narrow section of the shaft.

[0038] Thus, in accordance with the present invention, by controlling the relative lengths, wall thicknesses and material properties of the shaft sections, a club can be configured having the lightweight and vibration damping of a graphite shaft, as well as the wide range of bending stiffness properties and high torsional stiffness of a steel shaft without an excessively high swing weight. With respect to the comparison in Table 1, the club of the present invention has a very light total weight, a moderate D5 to E5 swing weight, excellent (variable) bending stiffness, excellent torsional stiffness, and excellent vibration dampening.

Problems solved by technology

Thus, stiffeners have the synergistic result of not only dampening vibration but also stiffening the club, particularly if disposed in the narrow section of the shaft.

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