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Iron-type golf club and frp shaft therefor

Iron-type golf club and frp shaft therefor description/claims

The present invention relates to an iron-type golf club, more particularly to a FRP shaft having a specific relation between the bending rigidity and weight of the shaft.

An optimum flexure of the golf club shaft during golf swing can accelerate the head speed just before impact and increase the dynamic loft angle at the impact. Thus, the launch angle of the ball can be optimized.

In the case of golfers with powerful right swings such as professional golfers and advanced golfers, usually, the head speed is high and the flexure during golf swing is large. Therefore, club shafts with relatively heavy weight and less flexibility (stiff) are conventionally used in iron-type golf clubs targeted at such users on the other hand, in the case of golfers with less powerful swings such as beginners and senior golfers, usually, the head speed is relatively low and the flexure is small. Therefore, club shafts with light weight and high flexibility are conventionally used in iron-type golf clubs targeted at such users. Thus, the club shafts of the conventional iron-type golf clubs are generally categorized into the above-explained two groups.

In recent years, on the on other hand, FRP club shafts made of fiber reinforced resins are widely used because the weight, bending rigidity and the like can be controlled easily in comparison with metal club shafts.

In the case that a golfer is not powerful but adept at the body turn or body spin on golf swing and thus the swing speed is high, if the golfer uses the former type of a club shaft with relatively heavy weight and less flexibility, then there is a tendency that the golf club can not come back to its right position at impact, thus the club face can not be squared and as a result the directions of the hit balls become unstable. If on other hand the golfer uses the later type of a club shaft with light weight and high flexibility, then there is a tendency that the club shaft is bent too much during golf swing, and as a result the club face can not be squared at impact and the directions of the hit balls become unstable.

It is therefore, an object of the present invention to provide an iron-type golf club and a club shaft therefor, which is suitable for beginners and senior golfers, and in which the directionality of the hit ball become stable, and at the same time, the golf swing power can be transferred to the club head at the maximum, without changing the current golf swing tempo.

According to the present invention, a club shaft for an iron-type golf club is made of a fiber reinforced resin, and has a per-39 inch weight W of not less than 30 grams and not more than 60 grams, and an average bending rigidity EIa of not more than 5.0 kgf sq.m, wherein an expression (1) EIa>=0.05 W+2.0 is satisfied. Preferably, an expression (2) EIa>=0.05 W+2.5 is satisfied. More preferably, an expression (3) EIa>=(1/15)W+2.0 is satisfied.

FIG. 1 is a front view of an iron-type golf club according to the present invention.

FIG. 2 is a diagram for explaining a method for measuring the bending rigidity of the club shaft.

FIG. 3 is a graph showing the ranges defined by the expressions (1), (2) and (3).

FIG. 4 shows a set of prepreg pieces which can be used to make the club shaft.

FIG. 5 shows prepreg pieces of the club shafts used in the undermentioned comparison tests.

Embodiments of the present invention will now be described in detail in conjunction with accompanying drawings.

• Provisional Patent
• Utility Patent

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