WO2001074458A1

WO2001074458A1 - Golf club shaft

Info

Publication number: WO2001074458A1
Application number: PCT/AU2001/000363
Authority: WO
Inventors: Mark Ashley Brown; Andrew Werner Last
Original assignee: Mark Ashley Brown; Andrew Werner Last
Priority date: 2000-04-03
Filing date: 2001-04-02
Publication date: 2001-10-11
Also published as: AUPQ662200A0

Abstract

A shaft for use in a golf club, the shaft having an elongate cross-sectional shape of fineness ration greater than one, and increasing in thickness from the leading edge to a maximum point and then decreasing in thickness to form a tapering afterbody.

Description

GOLF CLUB SHAFT

Field of the invention

The present invention relates to a golf club shaft, in particular an improved shaft that increases clubhead speed as the golf club is swung to hit a ball.

Background of the invention

In this specification, where a document, act or item of knowledge is referred to or discussed this reference or discussion is not an admission that the document, act or item of knowledge or any combination thereof was, at the priority date publicly available, known to the public, part of the common general knowledge, or known to be relevant to an attempt to solve any problem with which this specification is concerned.

Golf clubs are primarily composed of three elements - a head and a grip attached to either end of a shaft. A golfer commonly keeps a set of between 9 to 13 clubs, each designed to hit the ball a different distance, the set covering a range of about 280 metres (or more for professional golfers). In general, the longer the shaft length, the lesser the angle on the striking face (loft) of the club head, and the further a ball will travel when hit by the club.

The shaft is an elongate member that defines playability and consistency of the club. When the player swings the club, the action of the shaft can be described in terms of a 'slingshot'. During the back swing, the slingshot is loaded, then during the down swing, the energy stored in the slingshot is unloaded. The longer the shaft, the greater the energy stored, and the further the ball is propelled. The clubhead is designed with a particular loft to lift the ball off the ground. The greater the loft, the higher the trajectory of the ball and the less distance the ball travels. The evolution of golf ball design has to a large extent determined the distribution and design of the weight of clubheads, but from an efficiency standpoint, balance and overall weight of the head are most important. The grip provides a comfortable interface between the player's hands and one end of the shaft.

Since the early days of golf, club makers and the manufacturers of golf equipment have constantly sought to improve golf club or golf ball design to promote better scores.

Particular effort has been made to increase the performance of the shaft, mainly by changes to the materials of construction. In the earliest days of golf, clubs were handmade by craftsmen who relied on materials indigenous to their local region. These included native English and Scottish hardwoods such as ganga wood, greenheart, lemonwood, lancewood, purpleheart, ironheart, bulletwood, washaba, spit cane, orange wood, ash and bloomahoo. One early publication from 1687 mentions a Thomas Kincaid of Edinburgh as making shafts of hazel. By the first half of the 19 century, club makers had generally settled upon lemonwood, lancewood and ash for shaft making. Hickory was then introduced to Britain, possibly through trade with Russia or America. By the latter half of the 19^th century, hickory shafts had become particularly popular because they satisfied the club makers' requirements of lightness, the right degree of springiness with durability and resistance to warping. However, by the late 1800s it had become apparent that hickory shafts had four serious deficiencies; susceptibility to fatigue from overuse, a tendency to warp after play in bad weather, a lack of consistency from shaft to shaft and poor resistance to torsion.

Credit for invention of the first metal shaft goes to a Scottish blacksmith named Thomas Horsburgh who was granted UK patent 8603 (dated 1 May 1894) for a solid iron shaft. In an effort to keep the club weight at a range reasonably close to existing hickory shafted clubs, Horsburgh' s shafts were extremely small in diameter, but this had the effect of making the shafts unacceptably flexible for playing.

A flood of activity followed. In 1902 the Foster Brothers of Derbyshire sold shafts made from hickory that were supported by a series of steel wire ribs running up and down the shaft. While a type of steel shaft was developed in 1904, it was deemed too heavy and led to attempts in the early 1900 's to create a hollow steel shaft.

The earliest patent for the stepped tubuiar steel shaft in use today is US patent 976,267 (22 Nov 1910) issued to Arthur Knight of New York. Although the preferred embodiment of the patent was a shaft made as a straight tapered seamless steel tube, the patent does disclose a way of distributing the metal and form through a 'stepped' change in the tube's diameter. By the 1930's, steel shafts had virtually replaced hickory shafts.

To provide protection against corrosion, shaft companies developed a number of coatings, including chrome, copper, nickel plating and parkerizing, all with lacquering applied over the top. Some coatings were added to provide cosmetic appeal, including cellulose acetate sheathing incorporating a simulated wood grain effect. To offer different bending properties within the shafts, all sorts of shaft configurations appeared. Bell-bottom shafts, spiral-grooved shafts and double grooved shafts were just a few of the odd shapes that began to show up in the steel shafts of the 1930's. While touted by golf club manufacturers as a means of controlling bend point, these various 'corkscrews' and 'grooves' had little effect on the performance of the shafts.

In the 1950's, it was recognised that reduction in shaft weight was key to improving club performance. In 1954 Golfcraft of California introduced a shaft made from fiberglass laminated over a thin wall steel core to reduce weight but retain shaft strength. However the clubs met with limited popularity and production ceased. At the same time Burke Golf Co created an entirely fibreglass shaft made by double tube forming process, but the shaft exhibited extremely poor torsional resistance as well as less than adequate tensile strength. By the 1970's fibreglass shafts had been phased out. Similarly, lightweight aluminium shafts first developed in 1965 by LeFiell Products of California became popular in the late 1960's, but golfers did not like the soft feel of the shafts at impact and production had ceased by the early 1970's.

While the first composite shaft was patented in 1924, it was not until 1968 when Union Carbide was looking for a market for its new high-strength carbon fibres, that composites really took hold. The first shafts comprised fibres formed by being wrapped around a mandrel. By 1973 manufacturers had moved to using thin sheets of carbon fibres mixed with epoxy resin wrapped to form shafts. The initial popularity of the graphite shafts in the early 1970's faded due to the shaft's poor resistance to torque, and tendency to fracture. However, technological innovations such as using higher quality fiber and realignment of the sheets of graphite resin around the forming mandrel solved the fracture and torque problems.

Since the 1970's there have been numerous steps forward in producing lightweight steel shafts by decreasing wall thickness in low stress areas of the shaft, and utilising steel alloys such as chrome vanadium steel, which is lighter than carbon steel. There has also been a proliferation of inventions relating to shaft construction. For example Dynacraft uses their patented Bimatrx bond technology to combine high modulus graphite with a specially designed, high strength steel tip section. The ultralight properties of the graphite section create more club head speed to increase the distance covered by a ball. The exceptionally low torque value of the steel tip section provides more stability and thus more controlled ball flight with increased accuracy.

The 1990's has seen a repeat of the 1930's with attempts to change shaft geometry by incorporating 'bubbles', 'humps', 'bulges' and octagonal cross sections. The original bubble shaft patent dates from 1939 - the original having two bubble and the latest, only one. According to "The Modern Guide to Shaft Fitting" first published by Dynacraft golf in 1992 (accessible at hltpJ/www.dynacraftgolf.corn/PR/modguide.cfin) these geometric shafts have been developed in an effort to control the bending profile or weight distribution of the shaft. However all these shaft designs have adhered to shafts of circular cross- section, or shafts of symmetrical regular polygonal cross-section, closely approximating circular cross section.

Summary of the invention

It has now been found that the efficiency of a shaft can be increased by a specific improvement to the cross sectional shape.

The present invention therefore provides a shaft for use in a golf club, the shaft having an elongate cross-sectional shape of fineness ratio greater than one, and increasing in thickness from the leading edge to a maximum point and then decreasing in thickness to form a tapering afterbody. The fineness ratio is defined as the ratio of the chord of the cross section to the maximum thickness of the cross section. The cross sectional shape may be symmetric or alternatively asymmetric about the chord. In a particularly preferred embodiment, the two halves of the cross sectional shape are mirror images about the chord.

The cross sectional shape may vary along the length of the shaft, that is the cross section may vary to suit the chord at any point along the shaft. For example the degree of taper of the afterbody can be increased and/or decreased smoothly and continuously or abruptly along the length of the shaft.

The cross sectional shape may also be varied at the shaft/club head or shaft/grip interface. Usually the profile of the club includes a step where the club interfaces with the club head or grip, and this step affects the efficiency with which the club can be swung through the air. By appropriate variation of the cross sectional shape, the shaft may be fared into the club head to eliminate the step and improve shaft and overall club efficiency.

The shaft may be manufactured from any convenient material or combination of materials. The materials of construction may be chosen to customise shaft performance according to one or more of the standard industry tests for measuring individual shaft performance. These standard industry tests include; a. deflection testing - measuring the deviation of the shaft tip from the butt centerline after a known unit of force is applied to the tip to create a curve in the shaft; b. flex testing - measuring the shaft's stiffness based on its ability to resist bending; c. frequency testing - measuring the number of oscillations (measured in cycles per minute) a shaft makes over a known period of time after the tip is pulled down and released while mounted in a special frequency measuring device; and d. pattern testing - measuring the distribution of flexibility about the shaft.

For example, a shaft may be customised to satisfy the wide range of player body shape, styles and experience, from a beginner, through the ranks of club players, to a professional player.

The two major governing bodies of world golf have set down range limitations relating to some of these measurements although the limits sometimes differ between the two governing bodies. Designers of golf club shafts often prefer that their products comply with the limits set by one, or preferably both these bodies so that their products gain the widest possible acceptance amongst golfers.

In particular, both governing bodies currently require that for a given shaft the amount of deflection must not only fall within a certain range but must be constant in all directions. In a particularly preferred embodiment, the shaft of the present invention comprises a core member of circular cross section, enclosed by an outer member comprised of material that does not hinder the deflection of the core member. For example, the core member may comprise traditional stepped steel tube or graphite. The outer member may comprise a material of low density and high flexibility such as a carbon based polymer or silicon based polymer. Alternatively, the outer member may comprise a resilient skin with a gel intermediate the skin and the core. The present invention additionally provides a cover adapted for use with a conventional golf club shaft, the cover having an elongate cross-sectional shape of fineness ratio greater than one, and increasing in thickness from the leading edge to a maximum point and then decreasing in thickness to form a tapering afterbody, the cover defining a recess in which a conventional golf club shaft may be located. In use, the cover may.be slid along the length of the conventional shaft. Alternatively, the cover may have a longitudinal slit between the recess and outer perimeter of the cover, so the cover may be wrapped around a conventional shaft.

The shaft of the present invention can be applied to the full range of golf clubs including both the long-range 'woods' and shorter-range 'irons'. Given that the head of a club (excluding the putter) moves through the ball at 150 to 250 km/h, even a very small increase in efficiency of the shaft can cause a significant increase in club performance. Using the shaft of the present invention, efficiency can typically be increased to provide a further 3 to 6% in club performance, that is for example, an extra 7 to 15 metres of ball travel from a 5-wood struck off a tee.

Description of the drawings

The shaft of the present invention will now be described with reference to the following drawings in which

Figures 1(a) to 1(d) depict different plan forms of shafts according to different embodiments of the shaft of the present invention; and

Figures 2(a) to 2(g) depict examples of different cross sectional shapes of the shaft of the present invention.

Figure 1 depicts clubs having a shaft of constant chord (Figure 1(a)), increasing taper (Figure 1(b)), decreasing taper (Figure 1(c)) and a combination of tapers (Figure 1(d)). Figure 2 depicts six different cross sectional shapes (Figures 2(a) to (g)) of the shaft of the present invention when the club is swung towards a golf ball, that is, in the direction of the arrow. Figure 1(a) has been annotated to indicate the chord (CC) or longitudinal axis of the cross section, the thickness (BB'), the leading edge (C). In this depiction, it can clearly be seen that the ratio of the chord (CC) to the thickness (BB') is greater than one. The cross section increases in thickness from the leading edge (C) to a maximum (BB') and then decreases in thickness to form a tapering afterbody terminating at the following edge (C).

Figures 1(b) to 1(g) depict cross sections of differing rate of taper of the afterbody and differing leading edge radius. The cross sections of Figures 1(a) to 1(f) are symmetric about the chord (CC) while the cross section of Figure 1(g) is asymmetric. The word 'comprising' and forms of the word 'comprising' as used in this description and in the claims does not limit the invention claimed to exclude any variants or additions. Modifications and improvements to the invention will be readily apparent to those skilled in the art. Such modifications and improvements are intended to be within the scope of this invention.

Claims

THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS:

1. A shaft for use in a golf club, the shaft having an elongate cross-sectional shape of fineness ration greater than one, and increasing in thickness from the leading edge to a maximum point and then decreasing in thickness to form a tapering afterbody.

2. A shaft according to claim 1 wherein the cross-sectional shape has a chord about which the two halves of the shape are mirror images.

3 A shaft according to claim 1 wherein the cross-sectional shape is asymmetric about the chord.

4 A shaft according to any one of claims 1 to 3 wherein the cross sectional shape varies along the length of the shaft.

5 A shaft according to claim 4 wherein the degree of taper of the afterbody increases along the length of the shaft.

6 A shaft according to claim 4 wherein the degree of taper of the afterbody decreases along the length of the shaft. 7 A shaft according to any one of the preceding claims wherein the cross sectional shape is varied at the interface between the shaft and club head and/or the shaft and the grip.

8 A shaft according to any one of the preceding claims wherein the shaft deflection characteristics are essentially the same in all directions. 9 A shaft according to any one of the preceding claims wherein the shaft includes a core member of circular cross section, enclosed by an outer member comprised of material that does not hinder the deflection of the core member.

10 A shaft according to claim 9 wherein the core member is stepped steel tube or graphite. 11 A shaft according to claim 9 or 10 wherein the outer member is a carbon based polymer or silicon based polymer or combinations thereof.

12 A shaft according to claim 9 or 10 wherein the outer member includes a resilient skin with a gel intermediate the skin and the core. 13 A cover adapted for use with a conventional golf club, the cover having an elongate cross-sectional shape of fineness ratio greater than one, increasing in thickness from the leading edge to a maximum point and then decreasing in thickness to form a tapering afterbody, wherein the cover defines a recess within which a conventional golf club shaft may be located to form the shaft of any one of claims 1 to 12.

14 A golf club comprising a club head, a grip and the shaft of any one of claims 1 to 12.

15 A shaft for a golf club according to claim 1 and as herein described with reference to the drawings.