GB2313554A - Golf club shaft - Google Patents

Abstract

A metallic golf club shaft comprises a butt end 26, a tip end 24, and a generally tapering shaft 28, the shaft comprising near its butt end a cylindrical segment 44 of greater diameter than the diameter of the butt end or the remainder of the shaft and a transitional portion 50 which is tapered. A scheme for producing such a shaft from a uniform metal sleeve is also disclosed (Fig. 4 - not shown).

Description

GOLF CLUB AND SHAFT THEREFOR AND METHOD OF NAKING THE SHAFT This invention relates to a golf club and a shaft therefor and a method of making the shaft. More particularly, this invention relates to a golf club and to a metal shaft for the golf club wherein the shaft is formed with an enlargement along the length thereof to enhance the characteristics of the club during the use thereof in the playing of the game of golf. Further, this invention relates to a method of making the shaft with the enlargement formed therein.

Golf clubs typically are formed with a shaft of some length, with a club head secured to a tip end section of the shaft and with a grip secured to a butt end section of the shaft. The shaft is also formed with a central section which extends between the butt end section and the tip end section. Further, the shaft is typically formed from a metallic material such as, for example, steel or titanium, or from a non-metallic composite material such as, for example, graphite fibres embedded in an epoxy matrix.

The shafts which are used as a component of a golf club are typically tapered inward along the central section between the butt end section and the tip end section. Some metal shafts are tapered by forming a series of cylindrical sections of successively smaller diameters in the central section between the butt end section and the tip end section. This results in the formation of a series of successively smaller steps which appear as an overall taper in the outer surface of the shaft. Other metal shafts are formed with an inward taper between the butt end section and the tip end section with a smooth outer surface in the central section.

Due the structure of, and the materials used in, metallic shafts, each shaft tends to flex during the swinging of the associated golf club when used by a golfer in the playing of the game of golf. Over the years, the flexure of the shaft has become an important feature to which golfers relate by virtue of the "feel" which the golfers sense during use of the clubs. This provides a feedback to the discriminating golfer which allows the golfer to enhance the control of and to improve their playing of the game.

While flexure of the metal shaft is not necessarily a negative to the golfer, too much flexure, as well as too much stiffness, can have a undesirable effect on a particular golfers playing of the game. With this in mind, manufacturers of golf clubs and club shafts provide clubs having a variety of flexures, or stiffnesses, which allows each golfer, at their option, to seek and be fitted with the clubs which are best suited for the golfer.

In an effort to enhance the advantages of the flexure property of golf clubs with metal shafts, various modifications to the shaft have been attempted. One such modification included the formation of a lateral enlargement in the central section of the shaft to divide the shaft into two sections of flexation to thereby favourably vary the resultant "feel" experienced by the golfer. An example of a golf club and shaft of this type is disclosed in U.S. Patent No. 2,050,554.

While the lateral enlargement of the central section of the metal shaft as noted above effected the separation of the shaft into two sections, and thereby altered the "feel" of the club, further improvements are needed to provide todays golfer with a club which is economical to make and which further enhances the playability of the club.

Therefore, it is an object of this invention to provide a golf club and a metal shaft therefor which are economical to manufacture while improving the playability of the club.

Another object of this invention is to provide a golf club and metal shaft therefor which will enhance the playing of the game of golf by a golfer by establishing certain flexure and stiffness characteristics in the club and shaft.

The present invention provides a golf club, which comprises: a longitudinal metal shaft extending along an axis thereof and formed with a tip end section at one end thereof, a butt end section formed at the other end thereof and a central section formed between the tip end section and the butt end section; a club head mounted on and secured to tip end section of the shaft; a grip secured to the butt end section of the shaft; a first segment formed in the central section of the shaft which includes at least portions thereof which extend laterally from the axis of the shaft for a first prescribed distance greater than the distance any other portion of the shaft extends from the axis thereof; and a second segment formed in the central section of the shaft adjoining the first segment which includes at least portions which extend laterally from the axis of the shaft for a second prescribed distance which is less than the first prescribed distance.

The present invention further provides a metal golf club shaft extending along an axis thereof, which comprises: a tip end section formed at one axial end of the shaft; a butt end section formed at another axial end of the shaft opposite from the one axial end; a central section formed on the shaft between the tip end section and the butt end sect ion; a first segment formed in the central section of the shaft which includes at least portions thereof which extend laterally from the axis of the shaft for a first prescribed distance greater than the distance any other portion of the shaft extends from the axis thereof; and a second segment formed in the central section of the shaft adjoining the first segment which includes at least portions which extend laterally from the axis of the shaft for a second prescribed distance which is less than the first prescribed distance.

The present invention further provides a method of making a metal golf club shaft having a tip end section, a butt end section and a central section extending between the tip end and butt end sections with the tip end, butt end and central sections formed along an axis of the shaft, which comprises the steps of: forming a metal sleeve having a longitudinal axis with: a prescribed length and a prescribed uniform external diameter; a first opposite end section and a second opposite end section, each of which extend inward from opposite axial ends of the sleeve for a prescribed end distance and each being formed with a first prescribed wall thickness; and a central section of a prescribed central length between the opposite end sections with at least portions thereof being formed with a second prescribed wall thickness which is less than the first prescribed thickness; processing the sleeve to form in a selected portion of the central section thereof at least two adjacent cylindrical segments with successively smaller diameters each of which are less than the prescribed uniform external diameter; processing the selected portion of the central section by deforming the two cylindrical segments to form a generally smooth external tapered surface which tapers inward in an axial direction toward the first opposite end section; processing the sleeve to reduce the first opposite end section to a first-end uniform diameter which is less than the prescribed uniform external diameter; processing a portion of the central section spaced by a precise distance from the smooth tapered surface and located between the smooth tapered surface and the second opposite end section to form a uniform taper in the portion extending axially inward toward the second opposite end; and processing the second opposite end section to a second-end uniform diameter which is less than the first-end uniform diameter.

A preferred embodiment of a golf club and shaft will now be described with reference to the accompanying drawings, in which Figure 1 is a side view showing a golf club and a shaft therefor; Figure 2 is a side view of the shaft of Figure 1 showing structural features of the shaft; Figure 3 is a sectional view showing a sleeve or tube blank from which the shaft of Figure 2 is made; and Figure 4 is a block diagram showing the steps through which the tube blank is processed to form the shaft of Figure 2 from the tube blank of Figure 3.

Referring to Figure 1, a golf club 20 includes a shaft 22 having a tip end section 24, a butt end section 26 and a central section 28 joined between the tip end section and the butt end section, all aligned along an axis 30 of the shaft. A club head 32, shown in phantom, is secured to the tip end section 24 of the shaft 22 and a grip 34, shown in phantom, is secured to the butt end section 26 of the shaft.

The butt end section 26 is formed at a prescribed butt-end length, with a prescribed uniform external butt-end diameter and is generally cylindrical from an outboard end 36 to an inboard end 38 thereof. The tip end section 24 is also formed with a prescribed uniform external diameter which is less than the butt-end diameter. The tip end section 24 extends from an inboard end 40 to an outboard end 42 thereof for a prescribed tip-end length, which is greater than the butt-end length.

The central section 28 is formed with an enlargement 43 which includes a cylindrical segment 44 of a prescribed length near the inboard end 38 of the butt end section 26 which is formed with a first axial end 46 closer to the butt end section 26, and a second axial end 48 spaced from the first axial end and closer to the tip end section 24. The enlargement 43 further includes a tapered segment 50 which is formed in the central section 28 and extends between, and tapers inward from, the first axial end 46 of the cylindrical segment 44 to the inboard end 38 of the butt end section 26. The remaining portion of the central section 28 extends between, and tapers uniformly inward from, the second axial end 48 of the cylindrical segment 44 to the inboard end 40 of the tip end section 24. The enlargement 43 could be located axially at junctures along the central section 28 other than the preferred juncture illustrated in Figures 1 and 2 without departing from the spirit and scope of the invention.

Referring to Figure 2, various dimensions and parameters of the preferred embodiment of the shaft 22 are illustrated. In Table I, the wall thicknesses and the external diameter are shown at incremental distances along the length of the shaft 22 beginning at the outboard end 42 of the tip end section 24. For example, at a distance of 25.4 cm (10 inches) from the outboard end 42, the diameter is 0.94 cm (0.370 inch) and the wall thickness is 0.048 cm (0.019 inch). At 71.12 cm (28.0 inches) from the outboard end 42, the diameter is 1.74 cm (0.685 inch) and the wall thickness is 0.030 cm (0.012 inch).

It is noted that the preferred embodiment of the shaft 22 is 100.38 cm (39.5 inches) in length. Table I extends to 99 cm (39.0 inches). The diameter and thickness parameters for the distance of 100.38 cm (39.5 inches) from the outboard end 42, which distance is coincidental with the outboard end 36, is the same as the parameters shown in the Table I for the distance of 99 cm (39.0 inches) from the outboard end 42. Other dimensions and parameters for the shaft 22 could be used without departing from the spirit and scope of the invention.

Also, in the preferred embodiment, the shaft 22 is made of steel, but could be any other suitable metallic material such as, for example, titanium without departing from the spirit and scope of the invention.

As shown in Figure 3, a sleeve or tube blank 52, from which the shaft 22 is ultimately formed, is composed of a metal, such as steel, and is formed between opposite ends 54 and 56 with opposite end sections 58 and 60, a central section 62 and two transition sections 64 and 66. The parameters of the tube blank 52 are shown in Figure 3. It is noted that the illustration of the tube blank 52 in Figure 3 has been enlarged in comparison to the illustration of the shaft 22 in Figure 2 in order to fully reveal the structural features of the blank. The dimensions listed in each of Figures 2 and 3, and in Table I, provide the actual dimensional relationship between the tube blank 52 and the shaft 22 which is ultimately formed therefrom.

Referring to Figure 4, the tube blank 52 is initially formed by a drawbench 68 wherein a cylindrical tube 70 of uniform diameter is passed through a die externally thereof.

As the tube 70 is passed through the die, a nib located axially within the tube in the area of the die is selectively manipulated to alter the internal configuration of the tube blank 52 as the tube is being moved through the die to form the internal wall structure as shown in Figure 3. Thereafter, the blank 52 is processed through an annealer 72 to make the metal more workable in succeeding steps of the process. The annealed blank 52 is processed through a taper press 74 where, in successive die sink operations, four generally cylindrical segments of successively smaller diameters are formed in the section of the blank which ultimately forms tapered segment 50 in the shaft 22. The formation of the successively smaller segments presents a stepped configuration which tapers axially inward toward the end 54 of the blank 52, and ultimately toward the outboard end 36 of the shaft 22. The area of the four stepped cylindrical segments is then passed through a swage 76 to reshape the steps and thereby form a smooth tapered surface which forms the tapered segment 50 of the shaft 22 as shown in Figure 2.

The blank 52 is then passed through a reduction die 78 to reduce a butt portion of blank which ultimately forms the butt end section 26 to a diameter slightly greater than the ultimate diameter. The blank 52 is then processed through a swage 80 to form the butt end section 26 in its final diameter.

Thereafter, the blank 52 is processed through a taper press 82 where a plurality of cylindrical segments, for example, fourteen, are formed in the section of the blank which ultimately becomes the remainder of the central section 28. The segments are formed with successively decreasing diameters which taper axially inward from the portion of the blank 52 which ultimately forms the cylindrical segment 44 of the shaft 22 to the juncture of the blank which ultimately forms the inboard end 40 of the shaft 22. The partially formed blank 52 is processed through an annealer 84 to make the metal of the blank more workable. The partially formed blank 52 is processed through a swage 86 where the stepped cylindrical segments formed by the taper press 82 are reshaped to form the smooth surface of the tapered remainder of the central section 28 of the shaft 22. In addition, the portion of the blank 52 which forms the tip end section 24 is processed in the swage 86 to form the tip end section with a smooth surface and at the diameter shown in Figure 2. This completes the formation of the shaft 22.

In conventional metal shafts not formed with the enlargement 43, the shaft will flex from the outboard end of the tip end section to a flex point close to, and perhaps within, the butt end section. With clubs of this type, the club head strikes the ball at such a head orientation that the launch angle of the ball is comparatively low thereby limiting the travel distance of the ball. Also, with such flexibility, it is difficult to maintain the shaft in alignment as the head approaches the ball which results in a lack of accuracy in addressing the ball.

The enlargement 43 in the metal shaft 22 provides a facility for effectively dividing the shaft, and the club 20, into two sections whereby the butt end section 26 is much stiffer than the comparable section in the conventional club noted above. Also, the section of the shaft 22 and club 20 between the enlargement 43 and the head end of the shaft and club will be more flexible or whippy than the comparable section of the conventional club noted above.

This feature allows the retention of the same taper profile in the central section 28 of the shaft 22 as the taper profile in the comparable section of the conventional shaft.

Thus, the golfer will have the continued advantages characteristically found in a flexible club, but with the stiffer butt end section 26 the golfer will be able to better control the shaft alignment at the point of impact with the ball for improved accuracy leading to attainment of a comparatively higher launch angle and greater travel distance of the ball.

As noted above, in the preferred embodiment of the club 20 and the shaft 22, the enlargement 43 is formed by the cylindrical segment 44 and the immediately-adjoining tapered segment 50 with the preferred parameters of the segments as set forth in Figure 2 and in Table I. This combination of parameters for the segments 44 and 50, of the enlargement 43 for a shaft of 100.38 cm (39.5 inches) in length, provides the optimum structural stiffness for attaining the advantages of the invention as noted herein. Other combinations of parameters for the segments 44 and 50 could be used without departing from the spirit and scope of the invention.

Golf clubs typically are available in sets with each set including several drivers, which are referred to as "woods," and several other clubs referred to as "irons." Each club of a given set typically has a shaft which is of a length different from the length of any of the remaining clubs of the set. The preferred embodiment of the club 20 as described above, and as shown in Figures 1 and 2, includes a shaft which is 100.38 cm (39.5 inches) in length with the enlargement 43 precisely located as described and shown. Because of the different shaft lengths of the shafts of a given set of clubs, the enlargement 43 of each club could be located at a distance from the outboard end of the tip end section which is different from that distance of any other club in the set. However, in the preferred embodiments of each of the clubs of different lengths in a set, the enlargement 43 will be located adjacent the inboard end 38 of the butt end section 26 in the manner illustrated in Figures 1 and 2. As noted above, the enlargement 43 could be located at any juncture along the length of the central section 28 without departing from the spirit and scope of the invention.

Also, while the preferred embodiment of the shaft 22 with a length of 100.38 cm (39.5 inches) shows precisely the parameters of the adjoining segments 44 and 50 in combination with the precise location on the shaft, other combinations of parameters and location of the enlargement 43 could be used without departing from the spirit and scope of the invention.

L1 cm L1 in D cm D1 in t cm t1 in 0 0 0.94 0.37 0.053 0.021 2.54 1 0.94 0.37 0.053 0.021 5.08 2 0.94 0.37 0.053 0.021 7.62 3 0.94 0.37 0.05 0.02 10.16 4 0.94 1 0.37 0.05 0.02 12.7 5 0.94 0.37 0.05 0.02 15.24 6 0.94 0.37 0.053 0.021 17.78 7 0.94 0.37 0.048 0.019 20.32 8 0.94 0.37 0.051 0.02 22.86 9 0.94 0.37 0.046 0.018 25.4 10 0.94 0.37 0.048 0.019 27.94 11 0.94 0.37 0.046 0.018 30.48 12 1.0007 0.394 0.043 1 0.017 33.02 13 1.024 0.403 0.041 0.016 35.56 14 1.097 0.432 0.041 0.016 38.1 15 1.146 0.451 0.038 0.015 40.64 16 1.196 0.471 0.038 0.015 43.18 17 1.245 0.49 0.036 0.014 45.72 18 1.295 0.51 0.036 0.014 48.26 19 1.328 0.523 ( 0.033 0.013 50.8 20 1.392 0.548 0.033 0.013 53.34 21 1.442 0.568 0.033 0.013 55.88 22 1.494 0.588 0.033 0.013 58.42 23 1.544 0.608 0.03 0.012 60.96 24 1.595 0.628 0.03 0.012 63.5 25 1.646 0.648 0.028 0.011 66.04 26 1.7 0.67 0.029 0.0116 68.58 27 1.72 0.68 0.029 0.0115 69.22 27.25 1.74 0.685 0.03 0.012 71.120 28 1.74 0.685 0.03 0.012 71.76 28.25 1.74 0.685 0.032 0.0125 73.66 29 1.52 0.6 0.034 0.0135 76.2 30 1.52 0.6 0.036 0.014 78.74 31 1.52 0.6 0.036 0.014 81.28 32 1.52 0.6 0.037 0.0145 83.82 33 1.52 0.6 0.037 0.0145 86.36 34 1.52 0.6 0.37 0.0145 88.9 35 1.52 0.6 0.37 0.0145 91.44 36 1.52 0.6 0.37 0.0145 93.98 37 1.52 0.6 0.37 0.0145 96.52 38 1.52 0.6 0.37 0.0145 99.06 39 1.52 0.6 0.37 0.0145

Claims (3)

1. CLAIMS 1 A golf club, which comprises: a longitudinal metal shaft extending along an axis thereof and formed with a tip end section at one end thereof, a butt end section formed at the other end thereof and a central section formed between the tip end section and the butt end section; a club head mounted on and secured to tip end section of the shaft; a grip secured to the butt end section of the shaft; a first segment formed in the central section of the shaft which includes at least portions thereof which extend laterally from the axis of the shaft for a first prescribed distance greater than the distance any other portion of the shaft extends from the axis thereof; and a second segment formed in the central section of the shaft adjoining the first segment which includes at least portions which extend laterally from the axis of the shaft for a second prescribed distance which is less than the first prescribed distance.
2. 2 A metal golf club shaft extending along an axis thereof, which comprises: a tip end section formed at one axial end of the shaft; a butt end section formed at another axial end of the shaft opposite from the one axial end; a central section formed on the shaft between the tip end section and the butt end section; a first segment formed in the central section of the shaft which includes at least portions thereof which extend laterally from the axis of the shaft for a first prescribed distance greater than the distance any other portion of the shaft extends from the axis thereof; and a second segment formed in the central section of the shaft adjoining the first segment which includes at least portions which extend laterally from the axis of the shaft for a second prescribed distance which is less than the first prescribed distance.
3. 3 A method of making a metal golf club shaft having a tip end section, a butt end section and a central section extending between the tip end and butt end sections with the tip end, butt end and central sections formed along an axis of the shaft, which comprises the steps of: forming a metal sleeve having a longitudinal axis with: a prescribed length and a prescribed uniform external diameter; a first opposite end section and a second opposite end section, each of which extend inward from opposite axial ends of the sleeve for a prescribed end distance and each being formed with a first prescribed wall thickness; and a central section of a prescribed central length between the opposite end sections with at least portions thereof being formed with a second prescribed wall thickness which is less than the first prescribed thickness; processing the sleeve to form in a selected portion of the central section thereof at least two adjacent cylindrical segments with successively smaller diameters each of which are less than the prescribed uniform external diameter; processing the selected portion of the central section by deforming the two cylindrical segments to form a generally smooth external tapered surface which tapers inward in an axial direction toward the first opposite end section; processing the sleeve to reduce the first opposite end section to a first-end uniform diameter which is less than the prescribed uniform external diameter; processing a portion of the central section spaced by a precise distance from the smooth tapered surface and located between the smooth tapered surface and the second opposite end section to form a uniform taper in the portion extending axially inward toward the second opposite end; and processing the second opposite end section to a second-end uniform diameter which is less than the first-end uniform diameter.