Lightweight, durable golf club shafts

#The present invention relates to an ultra lightweight golf club shaft having excellent strength which includes a tapered section having a particular tapered design from a larger diameter to a smaller diameter. The shafts can either have a tapered section with a substantially constant reduction in diameter or a low angle stepdown design. More importantly, as disclosed herein, the configuration of the shafts makes them extremely durable even though they are much lighter in weight than conventional shafts. The lightweight shafts allow for a faster club head speed and thus can produce longer distance shots as well as better feel.

#Typical prior art golf club shafts are designed having a butt section, and a tip section interconnected by a tapered section, wherein the butt section has a larger outer diameter than the tip section. The butt and tip sections typically have a constant outer diameters throughout their length. The outer diameter is reduced between the butt section and the tip section by utilizing a step forming operation whereby a series of relatively steep step portions are introduced into the shaft tapered section along the length thereof. The diameter of the step portions become progressively smaller toward the tip end. Adjacent step portions are separated by narrow transitional areas having a stepdown angle of 8° when measured with respect to the longitudinal axis running through the shaft from the tip section to the butt section. However, it has been found that the use of the steep transitional portion angles result in several undesirable disadvantages, including creating a stress concentration area along the circumferential axis of the shaft at the transition area and a discontinuous stiffness along the length of the shaft. Accordingly, the shaft must be made relatively thick and heavy to overcome the stress concentration.

#It is generally known that an ideal golf club shaft should be of a minimal weight while concurrently being of a sufficient durability and stiffness to effectively allow all of the kinetic energy developed by the golfer to be transmitted to the golf ball. Heretofore, steel, or other metal, or non-graphite golf club shafts have been produced that are 95 grams or greater at traditional lengths of 40 and 41 inches or on average 2.38 and 2.32 grams/inch, respectively. In the prior art weight range, the average golfer cannot generate enough club head speed to produce much shaft flexing during the swing. Consequently, the average golfer cannot develop a proper feel for his clubs.

#The invention will be better understood and other features and advantages will become apparent by reading the detailed description of the invention, taken together with the drawings, wherein:

#FIG. 1 is a side elevational view of a golf club shaft according to the present invention wherein the tapered section has a plurality of constant diameter steps interconnected by tapered transition areas.

#FIG. 2 is a side elevational view of a golf club shaft having a tapered section which tapers at a substantially constant rate.

#The golf club shafts or shaft blanks of the present invention are formed from tubes of metal or a metal matrix composite. When utilized herein, tube generally refers to a hollow cylinder or pipe having a constant outer diameter. The inner diameter, and thus the transverse cross sectional thickness throughout the length of the tube, can be constant or vary in one or more areas. That is, the inner diameter and thus the wall thickness, can be varied throughout the length of the tube, and can even contain “cycles” or repeating patterns such as but not limited to sinusoidal cycles.

#The tube is generally considered a shaft after a process modifies, i.e. increases or decreases, at least a portion of the outer diameter so the same is no longer constant. The shaft is still a “tube” after being formed, albeit a specialized tubular blank having a special use. In the preferred embodiment, the shaft is manufactured from metal such as steel, titanium, aluminum, or alloys thereof. The shafts are preferably formed from 4140 m alloy steel available from manufacturers such as Worthington Steel of Pennsylvania. The shaft can also be a metal matrix composite as known in the art, wherein a matrix metal, such as but not limited to aluminum, surrounds or envelops fibers such as silicon carbide whiskers.

#Making reference now to the drawings, wherein like numerals indicate like or corresponding parts throughout the several figures, a golf club shaft prepared according to the present invention is shown in FIG. 1, and is generally designated 100. The shaft 100 includes a butt or grip section 110, a tip section 130, and a tapered section 120 therebetween. As is clear from the drawings, the butt, tip, and interconnecting tapered sections have a common, central longitudinal axis 140 extending therethrough.