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(11) | EP 1 393 782 A1 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | Golf club shaft set |
| (57) A set (34) of golf clubs (36-54) is provided including a plurality of shafts progressively
increasing in length. Each shaft includes a butt section (20) formed of a first material
coupled to a tip section (18) formed of a second, different material. The length of
each tip section (18) is inversely proportional to the overall length of the shaft
(16). As such, the tip sections (18) progressively decrease in length as the plurality
of shafts progressively increase in length (Fig. 3). |
FIELD OF INVENTION
[0001] The present invention relates to golf club shaft sets, and more particularly, to a golf club shaft set including shafts with composite first ends and metal second ends wherein the length of the metal tip end is inversely proportional to the overall length of the shaft.
BACKGROUND OF THE INVENTION
[0002] Two types of shafts dominate the golf club shaft market. The first type of shaft is made entirely of metal such as high strength alloy steel. The second type of shaft is made entirely of a composite such as graphite.
[0003] Metal shafts are generally regarded as being relatively heavy but provide high torsional stiffness. This results in a playability which yields accurate ball control and good feel but may limit club head speed and hence distance. It can also be made difficult to obtain a high tip flexibility with metal shafts compared to composite shafts which can compromise ball trajectory.
[0004] Composite shafts are generally regarded as being relatively light with more flexible tips which can result in a playability which yields higher club head speed and more distance as well as a higher ball trajectory. However, because composite shafts are not torsionally very stiff, composite shafts are also regarded as being somewhat limited in terms of accurate ball control and feel.
[0005] To take advantage of the separate benefits of metal and composite shafts while minimizing their deficiencies, a multiple material golf club shaft has recently been introduced to the market. A multiple material shaft is made partially of metal and partially of composite. In other words, a first portion of the shaft is formed of metal, a second portion of the shaft is made of composite, and the two portions are coupled together.
[0006] Multiple material shafts are generally regarded as being both lightweight and resistant to torque. This enables the generation of more club head speed than an all metal shaft and more accuracy than an all composite shaft. Nonetheless, it is still desirable to balance the need for distance and accuracy against one another across the entire multiple material shaft set.
[0007] For example, lighter and more tip flexible shafts are desirable in the long irons to provide more distance and higher ball trajectory at the expense of a certain degree of accuracy. In contrast, heavier and more torsionally stiff shafts are desirable in the short irons to provide more accuracy and feel at the expense of a certain amount of distance. Medium weight shafts with intermediate torsional stiffness are desirable in the middle irons to provide a compromise between distance and accuracy.
[0008] In view of the foregoing, it would be desirable to provide a multiple material golf club set specifically tailored to provide high club head speed in the long irons, high torsional stiffness in the low irons, and a compromise between the two in the middle irons.
SUMMARY OF THE INVENTION
[0009] A set of golf club shafts is provided including a plurality of shafts progressively increasing in length. Each shaft includes a butt section formed of a first material coupled to a tip section formed of a second, different material. Preferably, the tip section comprises metal while the butt section comprises composite. The length of each tip section is inversely proportional to the overall length of the shaft. As such, the tip sections progressively decrease in length as the plurality of shafts progressively increase in length. The relationship of tip length to butt length or overall length is maintained both in absolute and relative terms. For example, each tip section preferably decreases in length by about 0.5 inch from one club shaft to the next. The length of the tip section of the shortest shaft may be about 30-34 % of the entire length of the shaft whereas the length of the tip section of the longest one of the shafts may be about 18-20% of the entire length of the shaft.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein:
[0011] FIG. 1 is a side elevational view of a golf club shaft incorporating the teachings of the present invention;
[0012] FIG. 2 is a cross-sectional view of a metal/composite joint of the golf club shaft of FIG. 1; and
[0013] FIG. 3 is a side elevational view of a set of golf clubs incorporating the teachings of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0014] The following description of the preferred embodiments is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses.
[0015] The present invention is directed towards a set of golf club shafts wherein each shaft includes a composite butt section coupled to metal tip section. As each shaft of the set increases in length, the corresponding tip section decreases. This provides at least two advantages. First, because of the different specific gravities of composite material and metal, the longer metal tip maintains or even increases the weight of the shaft as the overall length decreases. Secondly, the increasing length of the metal tip provides more torsional stability as the shaft gets shorter.
[0016] Referring to FIG. 1, there is shown a golf club 10 having a grip 12, a head 14 and a tubular shaft 16. Although the club 10 is illustrated as a wood, it may also be an iron or a putter. The shaft 16 includes a tip section 18 and a butt section 20. The tip section 18 is preferably formed of a metallic material such as high strength steel while the butt section 20 is preferably formed of a composite material such as graphite. While the shaft 16 has been illustrated as having a smooth, tapered sidewall 22, it should be appreciated that a parallel or stepped sidewall could substitute therefore.
[0017] The tip section 18 is secured at a lower end 24 to head 14 by sizing it to fit standard club head hosel sockets. The upper end 26 of tip section 18 is telescopically and slidingly fit over the lower end 28 of the butt section 20. The physical characteristics of the tip section 18 from head 14 to the joint 30 where it meets the butt section 20, are designed to provide the desired balance of torsional stiffness, bending stiffness (flex), strength, and weight in order to yield the best playability when combined with the composite butt section. A preferred embodiment of such a joint 30 is described in U.S. Patent Application Serial No. 09/745,001 filed December 21, 2000 which is incorporated by reference herein in its entirety.
[0018] Turning now to FIG. 2, the joint 30 of FIG. 1 is illustrated in greater detail. An important aspect affecting the durability of the shaft 16 is the strength of the joint 30 between the metal tip section 18 and the composite butt section 20. As can be seen, the tip section 18 is in the form of a hollow metal cylinder and the butt section 20 is formed as a hollow composite cylinder. The butt section 20 includes a reduced diameter cylindrical portion or plug 32 for insertion into the tip section 18. The reduced diameter portion 32 may be formed during the lay-up of the composite butt section 20 or may be formed by grinding away a pre-selected annular amount of the butt material after initial formation. The reduced diameter portion 32 is dimensioned to ensure a sufficient overlap and durable interconnection with the tip section 18.
[0019] The metal tip section 18 and composite butt section 20 are joined together with an adhesive, such as epoxy bond 31. The thickness of the adhesive 31 is carefully controlled and the surface area of the tip section 18 and butt section 20 along the adhesive 31 is sufficient to ensure adequate strength. Bond strength is selected such that the joint 30 does not fail in shear from the torsional loads imposed through generally accepted levels of abuse while playing the game of golf. Limiting the maximum thickness of the adhesive 31 and increasing the surface area of the joint 30 also maintains the highest straightness standard for the assembled shaft 16.
[0020] Turning now to FIG. 3, the set of golf clubs 34 includes a 2-iron 36, 3-iron 38, 4-iron 40, 5-iron 42, 6-iron 44, 7-iron 46, 8-iron 48, 9-iron 50, and wedge 52. The set may also include a gap wedge, sand wedge, and lob wedge in addition to other club types. For example, the golf club shaft set could also include a 1 iron and/or one or more woods. The overall length of each shaft increases from the wedge 52 through the 2-iron 36. For example, the wedge 52 may have an overall length of 36.5 inches whereas the 2-iron 36 may have an overall length of 40.5 inches.
[0021] Each club in the set 34 preferably increases in length over the last consecutive shaft by about 0.5 inch. Conversely, each steel tip section 18 progressively decreases in length as the overall length of the corresponding shaft increases. Accordingly, the steel tip section 18 on the 40.5 inch 2-iron shaft 36 is about 7.5 inches. On the other hand, the steel tip section 18 on the 36.5 inch wedge shaft 52 is approximately 11.5 inches. This inverse relationship of tip length to shaft length continues throughout the shaft set 34
[0022] In a preferred embodiment of the present invention, each steel tip section 18 decreases in length by about 0.5 inch from the last consecutive tip section. To compensate for the decreasing length of the tip section 18 (and therefore maintain the desired overall length of the corresponding shaft), the length of the butt section 20 progressively increases as the plurality of shafts progressively increase in length. As such, the tip sections are not only inversely proportional (in length) to the overall shaft length, but also to the butt section length. This is true both in absolute and relative terms.
[0023] For example, in the shortest shaft, i.e., the wedge shaft 52, the tip section 18 accounts for approximately 30-33% of the entire length of the shaft. In contrast, in the longest shaft, i.e., the 2-iron 36, the tip section 18 accounts for about 17-19% of the entire length of the shaft.
[0024] The length of the tip section 18 not only corresponds to the overall length of the shaft, but also to the loft of the club head 14. The plurality of club heads 14 in the golf club set 34 progressively decrease in loft from the wedge 52 to the 2-iron 36. Correspondingly, the length of each tip section 18 progressively decreases as the loft of each club head 14 progressively decreases. In contrast to the inverse relationship described above with respect to club length, the relationship to loft is directly proportional.
[0025] While a full set of golf club shafts 34 is illustrated in Fig. 3, it should be appreciated that the term set as used herein could comprise as little as two golf club shafts. The only requirement of the set is that the first shaft is longer than the second shaft. In such a set, the first shaft includes a tip section which is shorter than the tip section of the second shaft.
[0026] The following table includes an exemplary set of golf clubs in a preferred set incorporating the teachings of the present invention:
| Iron | Total Shaft Length (inches) | Club Head Loft (degrees) | Tip Section Length |
| 2 | 40-41 | 15-19 | 7.0-8.0 |
| 3 | 39.5-40.5 | 18-22 | 7.5-8.5 |
| 4 | 39-40 | 21-25 | 8-9 |
| 5 | 38.5-39.5 | 24-28 | 8.5-9.5 |
| 6 | 38-39 | 28-32 | 9-10 |
| 7 | 37.5-38.5 | 32-36 | 9.5-10.5 |
| 8 | 37-38 | 36-40 | 10-11 |
| 9 | 36.5-37.5 | 40-44 | 10.5-11.5 |
| PW | 36-37 | 44-48 | 11-12 |
| GW | 36-37 | 48-52 | 11-12 |
| SW | 36-37 | 53-57 | 11-12 |
| LW | 36-37 | 58-62 | 11-12 |
1. A set of golf club shafts comprising:
a plurality of shafts (16) progressively increasing in length, each of said shafts (16) including:
a butt section (20), and
a tip section (18) coupled to said butt section (20), said tip section (18) being formed of a different material than said butt section (20),
characterized in that a length of each tip section (18) progressively decreases as said plurality of shafts progressively increases in length.2. The set of golf club shafts of claim 1, characterized in that a length of said butt section (20) progressively increases as said plurality of shafts
progressively increase in length.
3. The set of golf club shafts of claims 1 or 2, characterized in that a length of said tip section (18) of a shortest one of said shafts is about 30 -
33 percent of an entire length of said shortest one of said shafts.
4. The set of golf club shafts of anyone of claims 1 through 3, characterized in that a length of said tip section (18) of a shortest one of said shafts is between about
26,67 cm and 31,75 cm (10,5 and 12,5 inches).
5. The set of golf club shafts of anyone of claims 1 through 4, characterized in that a length of said tip section (18) of a longest one of said shafts is about 17 - 19
percent of an entire length of said longest one of said shafts.
6. The set of golf club shafts of anyone of claims 1 through 5, characterized in that a length of said tip section (18) of a longest one of said shafts is between about
16,51 and 21,59 cm (6.5 and 8.5 inches).
7. The set of golf club shafts of anyone of claims 1 through 6, characterized in that each tip section (18) progressively decreases in length by about 1,27 cm (0.5 inch).
8. The set of golf club shafts of anyone of claims 1 through 7, characterized in that said butt section (20) further comprises a composite material.
9. The set of golf club shafts of anyone of claims 1 through 8, characterized in that said tip section (18) further comprises a metal material.
10. A set of golf clubs comprising:
a plurality of club heads (14) progressively decreasing in loft;
a plurality of shafts (16) independently coupled to said plurality of club heads (14), each of said shafts (16) including:
a butt section (20); and
a tip section (18) coupled to said butt section (20), said tip section (18) being formed of a different material than said butt section (20);
characterized in that a length of each tip section (18) progressively decreases as said plurality of club heads (14) progressively decreases in loft.11. The set of golf clubs of claim 10, characterized in that a length of said butt section (20) progressively increases as said plurality of club
heads progressively decreases in loft.
12. The set of golf clubs of claim 10 or 11, characterized in that a length of said tip section of a shortest one of said shafts is about 30 - 33 percent
of an entire length of said shortest one of said shafts.
13. The set of golf clubs of anyone of claims 10 through 12, characterized in that a length of said tip section (18) of a shortest one of said shafts is between about
26,67 cm and 31,75 cm (10.5 and 12.5 inches).
14. The set of golf clubs of anyone of claims 10 through 13, characterized in that a length of said tip section (18) of a longest one of said shafts is about 17 - 19
percent of an entire length of said longest one of said shafts.
15. The set of golf clubs of anyone of claims 10 through 14, characterized in that a length of said tip section (18) of a longest one of said shafts is between about
16,51 and 21,59 cm (6.5 and 8.5 inches).
16. The set of golf clubs of anyone of claims 10 through 15, characterized in that each tip section (18) progressively decreases in length by about 1,27 cm (0,5 inches).
17. The set of golf clubs of anyone of claims 10 through 16, characterized in that said butt section (20) further comprises a composite material.
18. The set of golf clubs of anyone of claims 1 through 17, characterized in that said tip section (18) further comprises a metal material.
19. A set of golf clubs comprising:
a first shaft having a first length, the first shaft including a first butt section coupled to a first tip section, the first tip section being formed of a different material than said first butt section; and
a second shaft having a second length, the second shaft including a second butt section coupled to a second tip section, the second tip section being formed of a different material than said second butt section;
characterized in that said first shaft is longer than said second shaft and said first tip section is shorter than said second tip section.