Shaft For Conventional Golf Club

Abstract

A golf club shaft having an axis, an inner wall and an outer wall, both axial, circular in cross-section, a major portion of it adjacent to the club head tapering so as to narrow toward the head end of the shaft, the wall thickness thereby increasing. The shaft has throughout its entire length a substantially constant cross-section area in planes normal to the longitudinal axis thereby providing uniform linear distribution of the shaft weight throughout its length. The shaft may be expanded beyond an extension of the taper to form a handle, to which a lightweight wrapping may be applied as a grip.

Parent Case Text

CROSS-REFERENCE TO OTHER PATENT APPLICATION

This is a division of applicant's co-pending U.S. Pat. application Ser. No. 790,602, filed Jan. 13, 1969, entitled "Golf Club, Shaft and Head," and now U.S. Pat. No. 3,614,101.

Description

This invention relates to golf clubs.

Golf clubs are used in a classical sport which has acquired tradition and traditional preferences and attitudes over the years. Golf clubs with drastically altered envelope configurations may as well remain uninvented, because the risk of rejection by customers, and by professional and sporting organizations is very high. However, there remains a substantial opportunity to improve golf clubs, still remaining within a physical envelope which is very similar to conventional clubs. Such improved clubs require a completely new approach to the dynamics of the golf club in order to achieve their improved performances. The term "conventional" is frequently used in the specification and claims hereof to describe the envelope characteristics of the golf club of this invention. The adjective is intended to connote a club having a shaft with a head extending laterally from it so as to deliver a blow to a ball and exert a torque on the shaft at the time of impact. The term is used to exclude such non-conventional clubs as "croquet mallets." It also excludes extremely heavy clubs, contemplating a club whose weight lies roughly with in the limits of commonly accepted gross weights.

The general opinion in the golf club industry has long been that a golf club shaft should be springily flexible in order to deliver optimum power to the ball. However, this approach leads to considerable degradation of results, because springiness itself uses power which would better be applied to the ball. Furthermore, in order for a shaft to be springy, it must be relatively light, and this leads to two major problems. One problem is that of torque and bending of the tubular shaft. When these deflections occur, the face of the club will deflect from its true angle relative to the shaft and to the handle during its acceleration, and also will further deflect at the moment of impact. Both of these deflections fundamentally affect the accuracy of the blow delivered to the ball, and it is nearly impossible for anyone who is not a professional golfer accurately and regularly to compensate for them.

The other problem with light springy shafts resides in the necessary shear strength at the joint of the head and the shaft. The peek shear load at this point is quite great, so that considerable strength needs to be provided here, generally by a connector known as a "hosel," which is a tubular extension of the club head with a bore into which an end of the shaft is inserted. A heavy hosel requires an unfavorable weight distribution, and places substantial mass at a region substantially spaced from the point of impact with the ball. The resulting eccentric load causes still further deflection of the face at the moment of impact.

It is submitted that a correct theoretical dynamic model for a golf club is one wherein the head is supported by a weightless rigid shaft, with the mass of the head substantially evenly distributed over the head, and with a hosel of minimum length and mass. Prior to this invention, such a club was not attainable, because a shaft having the requisite strength in shear and torque at the head end could not be made within the established limits of total club weight. This invention provides a shaft of requisite shear and torsional strength, and which, especially when provided with lightweight means for a handle and grip, is substantially lighter than conventional shaft assemblies. It enables the hosel of the head to be lightened, and its eccentric weight reduced. This saved weight may then either be distributed over the club head further to improve the balance and power, or may be eliminated whereby to provide improved results for persons who do not possess the physical strength to manage the greater weight.

This invention comprehends both such a shaft, and a club incorporating it.

A shaft according to this invention comprises an elongated tubular member having an axis and an inner and outer wall. Major portions of both walls are tapered adjacent to the head end, and they narrow as they approach the head end. The wall thickness increases toward the head end. The lateral cross-sectional area remains substantially constant throughout the major proportion of the length of the shaft. As a result, a heavier-walled tube is provided at the head end to resist torsion and shear forces. The handle end, where such wall thickness is not required, has a thinner wall and a larger outer diameter, so that the grip may be formed of a simple wrapping, which is lighter than the conventional grip. Weight saved by these expedients may be distributed over the head where it contributes to the power of the blow. Furthermore, the handle may be formed as a conical portion of the shaft, thereby providing the benefit of a tapered grip.

A golf club head useful in this invention has a body with a striking face having an upper margin, and a hosel extending from the body. The hosel has a bore to receive the head end of the shaft, and this bore, and therefore the head end of the inserted shaft, extend to a region below an extension of the upper margin.

The above and other features of this invention will be fully understood from the following detailed description and the accomapnying drawings in which:

FIG. 1 is a side view partly in cutaway cross-section showing the presently preferred embodiment of the invention;

FIG. 2 is a cross-section taken at line 2--2 of FIG. 1;

FIG. 3 is a cross-section similar to that of FIG. 2, showing another embodiment of the invention;

FIG. 4 is an axial cross-section taken at line 4--4 of FIG. 3; and

FIG. 5 is a side elevation of a golf club head according to the prior art, and is another illustration of a conventional type of golf club.

A golf club 10, which is the presently preferred embodiment of the invention, is shown in FIG. 1. It comprises a shaft 11 and a head 12. The head includes a body 13 having a striking face 14, the striking face having an upper margin 15. An extension 16 of the upper margin, comprising an imaginary line, extends to the right in FIG. 1, and is a straight line.

As is customary in golf club heads, a hosel 17 is formed integral with the body and extends upwardly at the angle to which it is desired to have the shaft extend relative to the striking face. The hosel has a bore 18 therein, which bore extends below the extension of the upper margin, the term "below" referring to the direction toward the foot 19 of the club head.

A shaft 11 according to the invention has an axis 21, an outer wall 22, and an inner wall 23. The shaft has a handle end 24 and a head end 25. That portion of the shaft adjacent to the head end has properties specific to this invention, as will be more fully set forth below, said properties comprising the fact that the inner and outer wall are both tapered and their tapers narrow as they extend toward the head end. The term "taper" is not limited to a straight line taper. However, the taper preferably is substantially uniform and straight-line. The wall thickness of this portion of the shaft increases toward the said head end. Preferably, but not necessarily, the entire length of the shaft, except for a handle to be described, will similarly be tapered. However, the presently preferred processes used to form this shaft have certain economic criteria which make it convenient to form some portions spaced from the head end with a uniform cross-section and wall diameter.

A handle portion 26 (sometimes called a "handle end portion") is formed adjacent to the handle end. The handle portion may be used bare, but usually it is desirable to apply some covering thereto, because the club often becomes wet or slippery. Preferably, the handle portion is substantially conical. This creates a wedging action with the user's hands.

With standard clubs, it is necessary to put a relatively thick and heavy grip onto a relatively thinner shaft. However, by using an expanded shaft as shown, it is possible to use only a thin wrapping 28 as a grip, which may be ribbon-like in nature and quite light. This alone can save as much as one ounce of weight, which weight at this location could have significant deleterious effects on the golfer's results, and does do so on standard clubs. By utilizing a lighter grip such as a lightweight fabric wrapping, it is possible to take this saved weight and apply it to the shaft near the hosel to provide greater strength at that place without greater total club weight.

Because of the construction of this shaft, it is possible to use lightweight materials such as aluminum alloys and thereby provide a lightweight shaft with optimum strength where needed. By increasing the shaft strength adjacent to the hosel, but still utilizing thinner walls and lighter weight materials in the remainder of the tubular shaft, it is possible to remain within accepted total club weight standards by moving certain of the weight otherwise expected to be found in the club to the head itself. This is done by taking th weight eliminated from shafts and grips, and adding it to the club head, and also by shortening the hosel length and restructuring the head, as can be appreciated by a comparison of FIGS. 1 and 5. Alternatively, the weight saved may simply be eliminated. A player who does not have the strength or stamina to swing the larger club weight will find his performance improved with a lighter club of this design.

FIG. 5 shows a conventional club head 29 with a hosel 30, which hosel is substantially longer than the hosel of the present invention, and whose bore 31 stands generally above the upper margin 32 of striking face 33. It will be seen that this hosel configuration, which is required by the various parameters of prior art conventional club heads, adds considerable eccentric weight relative to the striking face, and requires a lessening of the weight of the striking portion of the head if the total club weight is to remain within accepted limitations. The redistribution of the weight (or reduced weight) in FIG. 1 is attained principally because of the adequacy of the strength of the joint between the hosel and the club shaft (because of the thicker cross-section at that point), the placing of the hoint closer to the striking face, and the reduction of the eccentric mass of the hosel. This enables an optimum club to be developed wherein strength characteristics are provided to the shaft with a lightweight handle, lightweight shaft, and club head with optimum distribution of mass in the striking face area which may have more mass than usual, if preferred.

Still another improvement on the shaft is possible by utilizing the construction shown in FIGS. 3 and 4 wherein inner wall 35 and outer wall 36 are provided which are basically circular in cross-section just as are walls 22 and 23 in FIG. 1. However, in this embodiment, the inner wall is modified by grooves 37 which are deepest at the head end and which may either extend for the full length of the shaft or instead and preferably may taper off to zero depth farther up the shaft. This creates longitudinally extending fins 38 which, for identical weight, will provide additional resistance to shear and torsion deflection. They are preferably formed during an extrusion operation and of self-material, as opposed to attached rod-like elements.

The shaft of this invention is best produced by drawing down a tube having initially larger inner and outer diameters. A useful technique is to begin with 1 inch or larger tubing and draw it to a normal 13/16 inch in order to trim up the wall thickness and to give some initial work-hardening to the material. Thereafter, the tube may be sequentially forced through a series of external forging dies with axial restraint on the tube. This causes a reduction in outer diameter, a lateral movement of the metal to create a thickening of the wall, and a reduction in inner diameter. There is permitted only negligible elongation, which is usually in the order of about 1 inch in an initially 44 inch long tube, which is the reason for the thickening of the wall. The results of this forging operation will be appreciated from an examination of FIG. 1 wherein it will be seen that substantially uniform linear distribution of the weight is likely, and that the cross-sectional area will remain substantially uniform from station to station. Of course, manufacturing tolerances will cause some small variations in this result, but it will ordinarily not be particularly great.

There are substantial advantages in the shaft, and in a golf club including the shaft, made according to the foregoing process. For one thing, it is possible by this means to achieve a ratio of wall thickness between that of the handle end to that of the head end on the order of 1: 2 1/2, the wall thickness at the head end being at least 250 percent that of the wall thickness adjacent to the handle end. Similarly, it will be noted from the table below that the diameter of the outer wall at the handle end will be at least 225 percent that of the diameter of the outer wall at the head end. Such a thickness ratio has not heretofore been attained and has severely limited the strength-weight ratio of shafts for golf clubs. By manufacturing the shaft with a forging process which substantially prevents axial growth while reducing the outer diameter, lateral metal movement with its favorable arrangement of grain structure and work-hardening is secured, together with a localized thickening of the wall where cross-sectional area is most needed. The result is an optimized shaft, and optimized club-shaft assembly.

In FIG. 1, one embodiment, related to the appended table of dimensions, has been shown. Station 0 is the handle end. The stations are in inches from that end, and the head end is station 44, the shaft thereby being 44 inches long. All other dimensions are also in inches. The club shown is a "driving iron."

The illustrated shaft may conveniently be made with only two forging dies, and will produce shafts suitable for a wide range of "iron" and "wood" club equivalents. A piece of reduced tubing as specified at about 13/16 inch outer diameter is reduced to form the handle portion 26, the remainder being reduced to the diameter of straight portion 41, this remainder being long enough to make the rest of the shaft. Then, starting at the proper dimension, tapered portion 40 is formed in another die. This other die may be longer or shorter as desired to make up the difference in length between the sum of the tapered portion and the handle portion, and the desired total length of the shaft.

If tooling cost is no object, then the full length of portions 40 and 41 will be tapered. The use of a straight portion does, however, provide significant economies.

Handle end portion 26 extends from about stations 0 to 11, with a taper of around 0.030 inches/inch after a short initial tubular length about 2 inches long. The straight portion 41 extends from about stations 11 to 19, with no taper. Tapered portion 40 (sometimes called a "head end portion") extends from about stations 19 to 44 with a taper on the order of about 0.009 to 0.010 inches/inch. The tapers referred to herein are those of the outer wall. The table shows measurements of an actual shaft, and as to be expected in swaging operations, there are minor variations from point to point. The cross-sectional areas given are calculated from the actual measurements utilizing the following formula:

A = .pi. (d/2 + r) (d/2 - r)

The dimensions are in inches and square inches as appropriate. A is the cross-sectional area; d is the outer diameter of the shaft; t is its wall thickness; and r is the diameter of the inside circle, i.e.,

r = (d - 2t)/2.

It will be noted that the club shaft is derived from an initially uniform tube by swaging the outer diameter to a tapered shape and limiting the axial growth of the material. The club is assembled by placing the shaft in the bore in the hosel and cementing it there with any suitable bonding material such as Loctite or any other suitable cement. This, too, enables one to avoid the undesirable weight of wrappings which are customarily used for such purposes.

The resu;ting club has a lightweight shaft which may advantageously be made out of lightweight alloys such as those of aluminum, magnesium, or titanium (however, other metals, including ferrous alloys, could also be used), which has substantial resistance to bending and torsion near the head end where such effects are important, which has the major portion of the weight in the club head instead of in the club handle, and which has a suitable integral handle with a lightweight grip. Because the handle and its wrapping are so light, the gross weight of the club may be made the same as that of a conventional club, but the weight saved in the handle may be placed in the head or the lower end of the shaft where it is more effective in driving the ball and resisting shear and torsion. The aluminum alloy known as 7178 can be used for the shaft which is the subject of this invention. The head may be of stainless steel. The result is an approach to the ideal club having a mass with its center of percussion in line with the striking face, with a lightweight, very rigid handle for swinging the club head. It has been found that clubs utilizing the shaft set forth in the table have given performances comparable to conventional woods of approximately the same total weight, but with greater accuracy and less effort on the part of the user, Such redistribution or reduction of weight has not heretofore been possible due to shapes required to provide torsional and shear strength at the hosel, much of which is due to the greater weight of the hosel itself. This invention thereby constitutes a stride toward the ultimate objective of a theoretically optimal golf club. It is useful for the entire member of the family of clubs from those commonly known as "woods" and "irons" to the putter itself, and has shown significant improvements and performance at all levels. It is evident that the dimensions may be changed, the major feature of the shaft residing in the tapered construction along a substantial axial length adjacent to the head end thereof, the term "substantial" in this regard meaning greater than 50 percent of the length of the shaft.

TABLE

Outer Wall Cross-Section Diameter(2r) Thickness(t) Area(A) Station (inches) (inches) (square inches) 0 .810 .027 .0664 1 .810 .027 .0664 2 .809 .028 .0687 3 .785 .028 .0666 4 .769 .028 .0652 5 .729 .030 .0659 6 .702 .032 .0673 7 .673 .0325 .0654 8 .645 .0335 .0643 9 .616 .035 .0639 10 .587 .037 .0639 11 .568 .039 .0648 12 .562 .039 .0641 13 .562 .039 .0641 14 .562 .039 .0641 15 .562 .039 .0641 16 .562 .039 .0641 17 .562 .039 .0641 18 .562 .039 .0641 19 .562 .039 .0641 20 .554 .039 .0631 21 .548 .040 .0638 22 .532 .041 .0632 23 .520 .042 .0631 24 .510 .043 .0631 25 .498 .044 .0627 26 .487 .045 .0625 27 .476 .047 .0633 28 .466 .048 .0630 29 .454 .051 .0645 30 .444 .053 .0651 31 .433 .053 .0633 32 .423 .055 .0636 33 .423 .057 .0655 34 .403 .059 .0638 35 .329 .061 .0634 36 .382 .063 .0631 37 .377 .064 .0629 38 .377 .065 .0637 39 .375 .065 .0633 40 .368 .068 .0641 41 .360 .069 .0631 42 .352 .071 .0627 43 .345 .073 .0624 44 .335 .077 .0624

What is claimed is:

Claims

1. A shaft for a conventional golf club comprising a continuous, homogenous metal tube having a longitudinal axis, a circularly sectioned inner wall and a circularly sectioned outer wall extending concentrically and axially along said axis from a head end to a handle end of said shaft, both of said walls, throughout a tapered head end portion extending from the head end to a substantial axial distance therefrom, and throughout a tapered handle end portion extending from a point adjacent to the handle end to a substantial axial distance therefrom, being continuously tapered, smooth and uninterrupted and respectively increasing and decreasing in diameter, the wall thickness of the shaft thereby increasing in both of said head end portion and of said handle end portion as the shaft extends toward the head end, the shaft having throughout its entire length a substantially constant cross-section area in planes normal to the longitudinal axis thereby providing uniform linear distribution of the shaft weight througout its length, the wall thickness at the head end being at least 250 percent that of the wall thickness adjacent to the handle end, and with the diameter of the outer wall of the handle end portion at its largest being at least 225 percent that of the diameter at

2. A shaft according to claim 1 in which the inner wall of the shaft is modified to include axially extending splines adjacent to the head end of

3. A shaft according to claim 1 in which an untapered portion is contiguous to, continuous with, and interconnecting the handle end portion and the

4. A golf club according to claim 1 in which the shaft is made of an

5. A shaft according to claim 1 in which a ribbon-like flexible, thin and light weight wrapping is wound around and upon the handle end portion.