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 Ser. No. 09/745,001 filed Dec. 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: 1

[0027] The description of the invention is merely exemplary in nature and, thus, variations that do not depart from the gist of the invention are intended to be within the scope of the invention. Such variations are not to be regarded as a departure from the spirit and scope of the invention.