1. Field of the Invention
The present invention relates generally to a shaft and a head for a golf club, and more particularly to a golf club shaft having an improved directionality at the time of a shot and a golf club head adapted to be connected to the golf club shaft.
2. Description of the Related Arts
A typical golf club shaft is of an overall length of 43 to 45 inches and is tapered with the head side diameter of about 8.5 mm for wood and about 9.4 mm for iron, and with the rear end diameter of about 15.0 mm for both. Due to the reduced diameter at its extremity, such a shaft has a higher flex and therefore is twisted to a large extent when the head tip or the heal hits a golf ball upon a shot, resulting in a poor ball directionality as well as a reduced carry.
Conceivable as measures for restricting the twisting of the shaft is to increase the thickness of a portion subjected to the stress or alternatively to reinforce the portion by means of a member having a higher rigidity. However, Such measures would give birth to a heavier overall weight or a greater shock and therefore permit only some advanced or powerful golfers to use the golf club.
For this reason, with the aim of improving the ball directionality and carry without reinforcing in particular the shaft itself, Japanese Utility Model Pub. No. Sho60-31743 discloses a shaft which is configured to be substantially straight from the tip to the rear end, with a taper within a range of 0/1000 to 4/1000 so as to secure the same diameter as the conventional shaft, thereby making the shaft itself flexible and reducing the diameter of the shaft as well as the air resistance at the time of a swing, to consequently ensure a faster head speed and therefore an improved carry. Japanese Utility Model Laid-open Pub. No. Sho62-59058 proposes a golf club shaft and a grip which are both configured to be straight so as to prevent a greater twisting action from occurring at a portion of the shaft in the vicinity of the head upon a shot and to inhibit an unstable orientation of the club face, thereby ensuring an easy control of the ball directionality as well as allowing the shaft flexure to appear overall without being localized only on the shaft tip side, to consequently achieve a greater restitution and an increase in carry.
It is however a fundamental premise for both that the shaft is flexible in the same manner as the conventional golf club shaft. It would therefore be essentially impossible to enlarge the diameter, which results in a lowered flex and a less shaft flexure. On the contrary, too small a shaft diameter in view of the sufficient shaft flexure will result in a lowered strength at the portion of the shaft in the vicinity of the head, so that a great twisting action may occur at the time of a shot depending on the position of the head which hits the ball, which will bring about an unstable orientation of the club face or a risk to damage the shaft itself. Thus, it was extremely troublesome to obtain a well-balanced shaft ensuring a proper strength at the portion of the shaft in the vicinity of the head as well as a good shaft flexure, since coordination must be made in consideration for materials and thickness of the shaft, the intensity of the golfer's force, etc.