JPH1157088A - Golf club shaft - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily provide timing and to improve directional property of hitted ball by providing successively a tip part, a shaft part and a bat part from one end part along the axial direction of a shaft and providing two expanded parts on the shaft part along the axial direction to give bending points at least at two positions. SOLUTION: A golf club shaft 1 has a tip part, a shaft part 3 and a bat part 4 from one end part along the axial direction and two expanded parts 3A and 3B are provided on the shaft part 3 along the axial direction. The first bending point PI and the second bending point P2 are respectively provided between these expanded parts 3A and 3B and between the expanded part 3B and the bat part 4, and the outer max. diameters Da and Db at the max. points (a) and (b) of the expanded parts 3A and 3B are respectively set within a range of 1.02-3.0 times the outer diameter of the shaft part 3. In addition, the lengths in the axial direction La and Lb of the expanded parts 3A and 3B are respectively set to be 5-40% of the length L of the shaft part 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a golf club shaft, and more particularly to a golf club shaft made of a fiber reinforced resin having high swing stability and high hitting direction.

[0002]

2. Description of the Related Art A golf club shaft made of a fiber reinforced resin using carbon fiber or the like is lighter in weight than a conventional steel shaft and has a longer flight distance, so that a shaft for a wood club or a shaft for an iron club is used. For example, the usage rate is increasing dramatically. Such a golf club shaft made of a fiber-reinforced resin is usually manufactured by a sheet winding method, an internal pressure molding method, or the like using a prepreg sheet in which fibers are impregnated with a resin. As the fiber constituting the prepreg sheet, carbon fiber, boron fiber, aramid fiber, titanium fiber and the like are used,
Various modified resins have been used as resins for impregnating fibers, and prepreg sheets used for golf club shafts are diversified. Therefore, it is possible to develop a golf club shaft having desired characteristics by combining different prepreg sheets.

For example, in a tapered golf club shaft whose diameter gradually increases from one end along the axial direction of the shaft, 1) a portion where the fiber direction forms a large angle with the axial direction of the shaft is provided. 2) A bending point is provided by providing a place where a prepreg sheet whose fiber direction is the same as the axial direction of the shaft is missing.

Further, a golf club shaft has been developed in which a metal having a high specific gravity, such as lead or tungsten, is filled near the tip of the shaft to adjust the shaft balance.

Further, in order to partially suppress the twist of the shaft, a prepreg sheet made of high elastic carbon fiber is crossed so that the fiber direction forms a predetermined angle (±) with respect to the axial direction of the shaft. Wound golf club shafts have been developed.

[0006]

However, the conventional tapered golf club shaft having the above-described provision of the bending point, the adjustment of the shaft balance, and the partial suppression of the twist has a high degree of freedom in design. There was a problem that was small. That is, since the shape of the conventional tapered golf club shaft is substantially determined, only a degree of freedom is allowed in which the type of carbon fiber, the resin content of the prepreg sheet, the configuration of the prepreg sheet, and the like are combined. Was. For this reason, there is a problem that any of the drawbacks such as poor grip of the ball, unstable directionality of the hit ball, poor swing-out, and difficulty in obtaining the timing of the swing, etc.

Further, a golf club shaft has been developed in which two overhangs are provided along the axial direction of the shaft, and a bending control unit is provided between the overhangs (Japanese Patent No. 26106).
No. 03046, U.S. Pat. No. 5,265,872, U.S. Pat. No. 5,620,380). In this golf club shaft, a combination of bending, hardness, and torque can be arbitrarily set by combining the relative length of the bending control portion or the thickness and diameter of both the bending control portion. However, the bending point is only one of the bending control sections provided between the two overhang portions, and is not yet sufficient as a golf club shaft having both swing stability and hitting direction. .

SUMMARY OF THE INVENTION The present invention has been made in view of such circumstances, and a golf club shaft capable of providing a golf club which is easy to take timing, swings well, and has excellent hitting directionality. The purpose is to provide.

[0009]

In order to achieve the above object, the present invention has a tip portion, a shaft portion, and a butt portion in order from one end along the axial direction of the shaft. Has two bulges along the axial direction,
In addition, the structure is such that at least two places have a bending point.

The present invention has a first flex point between the two bulges and a second flex point between the bulge and the butt.
A configuration having a bending point, a configuration having a first bending point between the tip portion and the bulging portion, and a configuration having a second bending point between the two bulging portions;
A configuration having a first bending point between the tip portion and the bulging portion and having a second bending point between the other bulging portion and the butt portion, between the tip portion and the bulging portion. Has a first flex point, a second flex point between the bulges, and a third flex point between the bulge and the butt.
The structure has a bending point.

Further, according to the present invention, the outer maximum diameter at the maximum point of the bulging portion is within a range of 1.02 to 3.0 times the outer diameter of the shaft portion near the butt portion side of the bulging portion. Configuration The length of one bulge in the axial direction is 5 to 40% of the length of the shaft.

In the present invention, at least two bending points are formed by the two bulging portions, and the bending points formed near the chip portion improve the grip of the ball and improve the hitting direction. The bend point formed near the butt part facilitates swinging down from the top and facilitates the creation of “tame”. The bend point formed in the middle part of the shaft is It has the effect of improving the pulling property,
The two bulges can change the mass distribution of the shaft depending on their position and size (weight), and the two bulges can change the torsional rigidity of the shaft depending on their position and shape.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The preferred embodiment of the present invention will be described.

FIG. 1 is a side view showing an embodiment of the golf club shaft of the present invention. In FIG. 1, a golf club shaft 1 has a tip portion 2, a shaft portion 3, and a butt portion 4 in order from one end along the axial direction of the shaft.

The tip portion 2 is a portion that is inserted into and fixed to the hosel of the club head, and includes a base shaft 11 described later. The shape of the tip portion 2 is usually a straight shape having the same outer diameter, but a tapered shape having a thin tip portion, an inverted tapered shape having a slightly thick tip portion, and the like.
Any of them may be used.

The butt portion 4 is connected to a base shaft 1 described later.
1 in the illustrated example, the end 4 on the shaft 3 side.
Although the outer diameter of the golf club shaft 1 has a tapered shape in which the outer diameter increases toward the end portion of the golf club shaft 1, the outer diameter may be a straight shape having the same outer diameter.

The shaft portion 3 is a characteristic portion of the golf club shaft 1 of the present invention, and includes a base shaft 11 described later.
And two bulging portions 3A and 3B along the axial direction of the base shaft 11, and the bulging portion 3A and the bulging portion 3B
And a second bending point P2 between the bulging portion 3B and the butt portion 4. Then, the first bending point P close to the chip portion 2
No. 1 has a pre-toning action to improve the grip of the ball and improve the hitting directionality during the swing. The second bending point P2 close to the butt portion 4 has an original tone function that makes it easy to swing down from the top and makes it easier to make a "tack". By the action of the bending points P1 and P2, the timing can be easily set and a rhythm can be given to the swing, and the shaft easily returns due to the recoil between the top and the impact. As a result, the acceleration is accelerated and the head speed is increased. Will be.

Here, the bulging portions 3A and 3B are portions having a maximum point in the distribution of the outer diameter of the shaft along the axial direction of the shaft. In the illustrated example, the bulging portion 3A has a maximum point indicated by an arrow. a, and the bulging portion 3B has a maximum point b indicated by an arrow. Note that the maximum points a and b are not narrow in the axial direction as in the illustrated example, but are described later in FIG.
It may have a certain width in the axial direction as shown in FIG. When the bulging portions 3A and 3B have a certain length along the axial direction within the following range, the bulging portions 3A and 3B may have any of a tapered shape and a straight shape having the same outer diameter. In the case of the taper shape, the maximum points a and b have a certain width in the axial direction as described above, and in the case of the straight shape, the maximum points a and b are located near the butt portion 4 of the bulging portions 3A and 3B. Will be.

The first bending point P1 and the second bending point P2 are portions that exhibit a smaller radius of curvature than the surroundings when the golf club shaft 1 is bent with a predetermined force. Incidentally, the bending is related to the bending rigidity EI (x). E of the bending rigidity EI (x) may be considered as Young's modulus, and I is a second moment of area. The golf club shaft of the present invention can vary the above E and I, and the variation width is large. However, the conventional tapered golf club shaft only changes E mainly, and the variation width Was narrower than the present invention.

The measurement of bending stiffness was carried out by the same applicant as in the present application by Japanese Patent Application Laid-Open Nos. 6-42954 and 6-105.
No. 934 and U.S. Pat. No. 5,429,008.

The external maximum diameter Da at the maximum point a of the bulging portion 3A is close to the butt portion 4 side of the bulging portion 3A (11).
a) The outer diameter of the shaft portion 3 is 1.02 to 3.0 times the outer diameter of the shaft portion 3, and the bulging portion 3B is one of the outer diameters of the shaft portion 3 near the butt portion 4 side of the bulging portion 3B (11b). .
It is preferable to set so as to be in the range of 02 to 3.0 times. In addition, the axial length La of the bulging portion 3A and the axial length Lb of the bulging portion 3B are set to be 5 to 40% of the length L of the shaft portion 3 of the golf club shaft 1. Is preferred.

The set positions of the bulging portion 3A and the bulging portion 3B in the shaft portion 3, namely, the distance L1 from the tip portion 2 to the bulging portion 3A, the bulging portion 3A and the bulging portion 3B
L2, the distance L from the bulging portion 3B to the butt portion 4
3 can be appropriately determined according to the set position and the number (2 or 3) of the bending points.

FIG. 2 is a side view showing another embodiment of the golf club shaft of the present invention having two bending points. In FIG. 2, the golf club shaft 1 'has a tip portion 2, a shaft portion 3, and a butt portion 4 in order from one end along the axial direction of the shaft. The shaft portion 3 includes a base shaft 11 described below and two bulging portions 3A and 3B along the axial direction of the base shaft 11.
It has. And it has the 1st bending point P1 between the tip part 2 and the bulging part 3A, and the 2nd bending point P2 between the bulging part 3A and the bulging part 3B. The first bending point P1 close to the tip portion 2 has a pre-toning action to improve the ball grip and improve the hitting direction during the swing. Also, a second bending point P2 formed in the middle of the base shaft 11
Has a medium tone effect of improving swing-out performance.

The golf club shaft of the present invention having two bending points includes a tip portion 2 and a bulging portion 3A.
Has a first bending point P1 between
A configuration having a second bending point P2 between B and the butt portion 4 is also possible. In this case, the first bending point P1 close to the tip portion 2 has a pre-toning action to improve the grip of the ball and improve the hitting direction during the swing, and the second bending point P1 close to the bat portion 4 The nari point P2 has an original tone function that makes it easy to swing down from the top and makes it easier to create “tame”.

FIG. 3 is a side view showing an embodiment of the golf club shaft of the present invention having three bending points. In FIG. 3, the golf club shaft 1 ″ is
It has a tip part 2, a shaft part 3, and a butt part 4 in order from one end along the axial direction of the shaft. Shaft part 3
Is provided with a base shaft 11 described later and two bulging portions 3A and 3B along the axial direction of the base shaft 11. Then, a first bending point P1 between the tip 2 and the bulge 3A, the bulge 3A and the bulge 3
B, a second bending point P2, and between the bulging portion 3B and the butt portion 4, a third bending point P3. The first bending point P1 close to the tip 2 is
At the time of a swing, it has a pretending effect of improving the grip of the ball and improving the directionality of the hit ball. The third bending point P3 close to the butt portion 4 has an original tone function of making it easy to swing down from the top and making it easy to make a "tack". And the base shaft 11
The second bending point P2 formed in the middle of the above has a medium tone action for improving the swing-out property.

FIG. 4 is a partial sectional view along the axial direction of the shaft portion 3 of the golf club shaft 1 of the present invention as shown in FIGS. The golf club shaft 1 shown in FIG. 4 is manufactured by a sheet winding method.
And the thick portions 12A and 12B constituting the bulging portion 3A and the bulging portion 3B.
It consists of

The base shaft 11 is formed by laminating resin layers containing fibers. The fiber is carbon fiber,
Polyamide fibers, boron fibers, metal fibers, glass fibers, and unidirectional fibers composed of two or more of these fibers, woven fibers, braided fibers, and nonwoven fibers can be used. Also, as the resin, epoxy resin,
Melamine resin, phenolic resin or thermoplastic nylon,
Polycarbonate resin, polyphenylene sulfide resin, polyetheretherketone resin, polyetherimide resin, and the like can be used. For example, the inner layer side of the base shaft 11 may be a high elastic fiber reinforced resin layer and the outer layer side may be a high strength fiber reinforced fiber layer, or all layers may be formed of a high strength fiber reinforced fiber layer. It can be set appropriately. The thickness t of the base shaft 11 is
It is preferable to set in the range of 0.4 to 3.0 mm,
Further, the shape of the portion corresponding to the shaft portion 3 of the base shaft 11 may be either a straight shape having the same external diameter or a tapered shape having a thin tip portion 2 side.

The thick portions 12A and 12B are also formed by laminating resin layers containing fibers. The above-mentioned thing can be mentioned as a fiber and resin which comprise. The thicknesses of the thick portions 12A and 12B can be set so as to form the bulging portions 3A and 3B having the above-described shapes. In the illustrated example, the cross-sectional shape of the thick portions 12A, 12B is such that the maximum thickness Ta,
Tb, the thickness of which is gradually reduced on both sides, but is not limited to this. For example, as shown in FIG. 5, the maximum points a,
b may have a certain width along the axial direction, and the thickness may gradually decrease on both sides.

The golf club shaft of the present invention manufactured by the sheet winding method may have a cross-sectional structure as shown in FIGS.

In FIG. 6, the shaft portion 3 includes a base shaft 11 extending over the entire length of the golf club shaft 1.
The base shaft 11 has an inner layer 11a and an outer layer 1
1b, and has a structure in which thick portions 12A and 12B are formed between the inner layer 11a and the outer layer 11b at locations where the bulging portions 3A and 3B are provided.

In FIG. 7, the shaft portion 3 has a base shaft 11 which extends over the entire length of the golf club shaft 1, and the portion of the base shaft 11 where the bulging portions 3A and 3B are provided is provided. This is a structure in which thick portions 12A and 12B are formed inside.

In the golf club shaft 1 shown in FIGS. 6 and 7, the cross-sectional shape of the thick portions 12A, 12B is also changed to the maximum points a, b of the bulging portions 3A, 3B as shown in FIG. Have some width along the axial direction,
The thickness may be gradually reduced on both sides.

FIG. 8 is a partial sectional view along the axial direction of the shaft portion 3 of the golf club shaft 1 of the present invention as shown in FIGS. The golf club shaft 1 shown in FIG. 8 is manufactured by an internal pressure molding method.
The golf club shaft 1 has a base shaft 11 extending over the entire length thereof, and bulging portions 3A and 3B are formed at two predetermined positions of the base shaft 11.
The base shaft 11 is formed by laminating resin layers containing fibers. As the fibers, use carbon fibers, polyamide fibers, boron fibers, metal fibers, glass fibers, and unidirectional fibers composed of two or more kinds of these fibers, woven fibers, nonwoven fibers, braided fibers, and the like. Can be. Also, as the resin, epoxy resin, melamine resin,
Phenol resin, thermoplastic nylon, polycarbonate resin, polyphenylene sulfide resin, polyetheretherketone resin, polyetherimide resin and the like can be used. For example, the inner layer side of the shaft portion 3 may be a high-elasticity fiber-reinforced resin layer and the outer layer side may be a high-strength fiber-reinforced fiber layer, or all layers may be formed of a high-strength fiber-reinforced fiber layer. It can be set appropriately.
The thickness t of the base shaft 11 of the shaft portion 3 is 0.3
It is preferable to set in the range of ~ 5.0 mm,
The shape of the shaft portion 3 (base shaft 11) other than the bulging portions 3A and 3B may be any of a straight shape having the same outer diameter and a tapered shape having a thin tip portion 2 side.

The cross-sectional shapes of the bulging portions 3A and 3B are such that the outer diameter becomes maximum at the local maximum point a and the local maximum point b, and the external diameter gradually decreases on both sides, but is not limited thereto. Not something. For example, FIG.
As shown in the figure, the maximum points a, b of the bulging portions 3A, 3B
May have a certain width along the axial direction, and the outer diameter may gradually decrease on both sides.

As described above, the golf club shaft of the present invention has at least two bending points formed by the two bulging portions. Therefore, the bending points formed near the tip portion improve the grip of the ball. It has the effect of increasing the direction of the hit ball, and the bending point formed near the bat part makes it easy to swing down from the top,
It has the effect of making it easier to create "tame", and the bend point formed in the middle part of the shaft has the effect of improving the swing-out property. Such an effect is made possible by satisfying the constituent requirements of the present invention. .

For example, as shown in FIG. 10, one bulging portion 23A is provided on the tip portion 24 side of the base shaft 22.
In the golf club shaft 21 having the bending point P1 between the bulging portion 23A and the butt portion 25,
Since there is only one bending point P1 substantially at the center of the shaft, it is medium-tone and can only provide the effect of good swing-out.

As shown in FIG. 11, in the golf club shaft 31 having one bulge 33A slightly near the center from the tip portion 34 of the base shaft 32, the first recess is provided on the tip portion 34 side. It has a bending point P1, and has a second bending point P2 between the bulging portion 33A and the butt portion 35. Therefore, it is possible to provide a pre-tone effect and a medium-tone or original tone effect. However, since only one bulging portion is provided, it is difficult to freely set the position of the second bending point P2 between the bulging portion 33A and the butt portion 35, and the setting range is narrow. It will be. On the other hand, for example, in the golf club shaft of the present invention shown in FIG. 2, the position of the second bending point P2 can be freely set by moving the position of the bulging portion 3B. That is, in the state shown in FIG. 2, a pre-tone effect and a medium-tone effect are obtained, and by moving the position of the bulging portion 3 </ b> B toward the butt portion 4, the pre-tone effect and the original tone effect are obtained. An effect can be produced.

In the present invention, in addition to the above-described effects, the position and size (weight) of the two bulges are appropriately set to change the mass distribution of the shaft and adjust the shaft balance. And the effect that the torsional rigidity of the shaft can be changed by appropriately setting the positions, shapes, and the like of the two bulging portions.

For example, by moving the positions of the two bulging portions of the golf club shaft of the present invention shown in FIG. 1 to the butt portion 4 as shown in FIG. 2, the mass distribution changes, and the shaft balance is changed. Can be shifted to the butt portion 4 side. Thus, according to the present invention, the tip 2
The head can be made lighter by providing the bulging portion closer to the side, and the head can be made heavier by providing the bulging portion closer to the butt portion 4 side. The same effect can be obtained by changing the size (weight) of the bulging portion.

The mass distribution can be measured by the measuring method and measuring apparatus described in Japanese Patent Application Laid-Open No. Hei 8-215349 and US Patent Application No. 08/599784 filed by the same applicant as the present application.

The golf club shaft of the present invention shown in FIG. 1 has two bulging portions located closer to the tip portion 2 than the golf club shaft of the present invention shown in FIG. The torsional stiffness on the two sides is significantly higher. In the present invention, the torsional rigidity of such a shaft can be adjusted also by the shapes (thickness, length) of the two bulging portions. Here, the torsional rigidity is G
Ip (x), G is the shear modulus, and Ip is the secondary moment of area. In the golf club shaft of the present invention, G and Ip can be largely varied by providing two bulges and appropriately setting the positions and shapes thereof. Therefore, a golf club shaft having significantly higher torsional rigidity (less torsion) at a desired position than a conventional tapered golf club shaft can be obtained.

The torsional rigidity can be measured by the measuring method and measuring apparatus described in Japanese Patent Application No. 8-25669 and US Patent Application No. 08 / 797,299 filed by the same applicant as the present application.

Next, the production by the sheet winding method will be described using the golf club shaft of the present invention having a sectional structure as shown in FIG. 4 as an example.

First, the base shaft 11 is placed on the mandrel.
Wind a prepreg sheet to form The prepreg sheet to be used is a material obtained by impregnating a fiber with a resin, and a material obtained by orienting a reinforcing fiber at a desired angle with respect to an axial direction of a shaft can be used. Use prepreg sheets.

Next, a prepreg sheet for forming the thick portions 12A and 12B is disposed at a desired position on the fiber reinforced resin prepreg sheet. The prepreg sheet to be used may be one in which reinforcing fibers are oriented at a desired angle with respect to the axial direction of the shaft.

Thereafter, the resin of each prepreg sheet is cured by heating, and the mandrel is pulled out to obtain the golf club shaft of the present invention.

Next, the production by the internal pressure molding method will be described using the golf club shaft of the present invention having a sectional structure as shown in FIG. 8 as an example.

First, a prepreg sheet for forming the base shaft 11 is wound around a mandrel having a hollow structure having an air injection hole on the surface thereof through an elastic tube. As the prepreg sheet to be used, a fiber reinforced resin prepreg sheet in which reinforcing fibers are oriented at a desired angle with respect to the axial direction of the shaft can be used, and usually, a plurality of types of fiber reinforced resin prepreg sheets are used.

Next, after the prepreg sheet wound around the mandrel is set in a molding die, air is injected from the air injection holes of the mandrel to apply internal pressure to the prepreg sheet, press it against the molding die, and heat it. Then, each prepreg sheet is thermoformed, and then the mandrel and the stretchable tube are pulled out, whereby the golf club shaft of the present invention is obtained.

[0050]

Next, the present invention will be described in more detail with reference to examples. (Example) A golf club shaft having a sectional structure as shown in FIG. 4 was manufactured by a sheet winding method.

First, a fiber reinforced resin prepreg sheet (HYEJ17K700-35 (manufactured by Mitsubishi Chemical Corporation) with a carbon fiber oriented at 0 ° (the mandrel axis direction is set to 0 °, the same applies hereinafter) impregnated with epoxy resin). 0.17m
m)) was wound around the tip portion of the mandrel in five layers to form a reinforcing portion. The mandrel used had a step with a reduced diameter at the tip portion, and the shaft portion and the butt portion had a tapered shape that became thicker toward the butt side end of the mandrel. A larger mandrel was used.

Next, a fiber-reinforced resin prepreg sheet (P3055-12 (0.12 mm in thickness) manufactured by Toray Industries, Inc.) in which high-strength carbon fibers oriented at ± 45 ° were impregnated with epoxy resin was used. 3 layers on tip side, 2 on bat side
It was wound around a mandrel to form a layer.

Next, a fiber reinforced resin prepreg sheet made by impregnating a carbon fiber oriented at 0 ° with an epoxy resin in a chip portion (HYEJ12K700-35 manufactured by Mitsubishi Chemical Corporation)
(Thickness: 0.12 mm)).

Next, two layers of a fiber-reinforced resin prepreg sheet (P3055-10 (0.10 mm thick) manufactured by Toray Industries, Ltd.) impregnated with epoxy resin in high-strength carbon fibers oriented at 0 ° from above. And a fiber reinforced resin prepreg sheet obtained by impregnating high-strength carbon fibers oriented at 0 ° with an epoxy resin (P3055-manufactured by Toray Industries, Inc.)
12 (thickness 0.12 mm)) was wound in two layers.

Thus, the winding of the prepreg sheet for the base shaft is completed.

Next, a trapezoidal shape in which high-strength carbon fibers are impregnated with an epoxy resin (base 170 mm, top 20 mm,
430 mm high) fiber reinforced resin prepreg sheet (P3055-12 (0.12 mm thick) manufactured by Toray Industries, Inc., 0
° orientation)) to form a first bulge (closer to the tip) so that the bottom is parallel to the axial direction of the mandrel. Also, a trapezoidal (180 mm bottom, 20 mm top, 430 mm height) fiber reinforced resin prepreg sheet (Toray Industries, Inc.) in which high-strength carbon fibers are impregnated with epoxy resin at desired positions on the base shaft prepreg sheet. P3055-12 (0.12mm thickness), 0 °
The orientation)) was wound so that the bottom was parallel to the axial direction of the mandrel to form a second bulge (closer to the butt).

Thereafter, the preform obtained by winding the prepreg sheet around the mandrel as described above is heat-cured, the mandrel is pulled out, and both ends are cut so as to have a size of 914 mm. (Example) was produced. The dimensions (see FIGS. 1 and 4) of each part of the golf club shaft were as follows.

L: 614 mm L1: 27 mm L2: 99 mm L3: 139 mm La: 170 mm Lb: 179 mm Distance from tip end to maximum point a: 151 m
m ・ Distance from the maximum point a to the maximum point b: 281m
m ・ Distance from the maximum point b to the rear end of the butt part: 482m
m ・ External diameter Da of the maximum point a: 11.8 mm ・ External diameter Db of the maximum point b: 13.6 mm ・ External diameter of the base shaft (tapered shape) of the tip portion: minimum 9.44 to maximum 9.45 mm ・ shaft External diameter of base shaft (tapered shape) of part: minimum 9.45 to maximum 13.9 mm External diameter of base shaft (tapered shape) of butt part: minimum 13.9 to maximum 19.1 mm The above golf club shaft ( Example 1) is between the two bulging portions (at a position of 202 mm from the tip of the tip portion),
In addition, there were a total of two bending points between the butt portion and the second bulging portion (a position 646 mm from the tip of the tip portion). Comparative Example 1 A tapered golf club shaft was manufactured by a sheet winding method.

That is, a preform having a prepreg sheet wound around a mandrel was prepared using the same mandrel as in the example and in the same manner as the winding of the prepreg sheet for the base shaft in the example. Thereafter, the preform was thermally cured, and the mandrel was pulled out to remove 914 m.
The golf club shaft for an 8th iron club (Comparative Example 1) was produced by cutting both ends so as to obtain m.

The dimensions of each part of the golf club shaft were as follows.

External diameter of shaft (taper shape) (excluding butt portion): minimum 9.44 to maximum 13.9 mm External diameter of shaft butt portion (taper shape)
: Minimum 13.9 to maximum 19.1 mm The golf club shaft (Comparative Example 1) had a bending point at a position 250 mm from the tip of the tip portion. (Comparative Example 2) A golf club shaft (Comparative Example 2) in the same manner as in Example 1 except that the bulging portion is provided only at one position near the tip portion and the forming position is as described below.
Was prepared.

L1: 10 mm La: 180 mm Distance from tip of tip to maximum point a: 195 m
m ・ External diameter Da of maximum point a: 12.7 mm The above golf club shaft (Comparative Example 2) has one bending point between the butt portion and the bulging portion (at a position 360 mm from the tip of the tip portion). Met.

The radius of curvature and bending stiffness of the golf club shafts (Example, Comparative Examples 1 and 2) by bending were measured, and the results are shown in FIG. 12 (indicated by the reciprocal of the radius of curvature) and FIG. Was.

As shown in FIG. 12, in the embodiment, there are two portions having small curvature radii (portions indicated by P1 and P2 in the drawing), and it is confirmed that the bending point is two. As shown in FIG. 13, there are also two portions having low bending stiffness (portions indicated by arrows) corresponding to FIG.

On the other hand, in Comparative Example 1, it was confirmed that there was one portion having a small radius of curvature (the portion indicated by P 'in the drawing), and it had one bending point. As shown in FIG. 13, there is also one portion having low bending rigidity.

Further, in Comparative Example 2, it was confirmed that there was one portion having a small radius of curvature (the portion indicated by P ″ in the drawing), and that one bending point was obtained. As shown in FIG. 13, there is also one portion having low bending rigidity.

Next, a head (weight 285 g) for an iron club was mounted on the tip portion of the golf club shaft (Example, Comparative Examples 1 and 2) manufactured as described above. A grip (weight 50 g) was attached to the butt. For each such iron club (8th), a professional golfer's tester was used to perform five actual hit tests, and the flight distance (carry), directionality, and swing stability were measured and evaluated. The results are shown in Table 1 below. In addition, the flight distance was shown by the average value of five times. In addition, the directionality and the swing stability were evaluated based on the following criteria.

Evaluation criteria of directionality ：: The ball flew in the target direction in all five actual hits Δ: Of the five actual hits, the ball flew in the target direction three to four times ×: 5 Of the actual hits, the ball flew in the target direction no more than two times. Evaluation criteria for swing stability ：: Good swing and easy timing △: Easy swing and easy timing Either one of them is insufficient. ×: Both the swing-out property and the ease of timing are insufficient.

[0069]

[Table 1] As shown in Table 1, it was confirmed that the iron club using the golf club shaft of the present invention (Example) had excellent swing stability and ball direction stability.

On the other hand, the iron club using the tapered golf club shaft (Comparative Example 1) is inferior in the flight distance as compared with the embodiment, and has good hitting direction stability but insufficient swing stability. Met. Further, the iron club using the golf club shaft having one bulging portion and one bending point (Comparative Example 2) has the hitting distance stability and the swing stability, although the flight distance is close to that of the embodiment. It was not enough.

[0071]

As described in detail above, according to the present invention, the tip portion is arranged in order from one end along the axial direction of the shaft.
It has a shaft portion and a butt portion, and the shaft portion has two bulging portions along the axial direction and has at least two bending points. The formed bending points improve the grip of the ball and give good hitting direction, and the bending points formed close to the bat make it easy to swing down from the top and easily create "tame" Also, the bend point formed in the middle part of the shaft gives excellent swing-out performance, which makes it easy to take timing and gives the rhythm to the swing, and the shaft is rebounded from top to impact The ball is likely to return, resulting in acceleration and increased head speed, and excellent flight distance, swing stability and hitting ball directionality. Golf club is possible. Further, since the mass distribution of the shaft can be changed by appropriately setting the position and size (weight) of the two bulging portions, the adjustment of the shaft balance is easy and the adjustment width is large. The torsional rigidity of the shaft can be freely changed by appropriately setting the position and the shape of the bulging portion, and the degree of freedom in designing the club is greatly improved as compared with the conventional club.

[Brief description of the drawings]

FIG. 1 is a side view showing one embodiment of a golf club shaft of the present invention.

FIG. 2 is a side view showing another embodiment of the golf club shaft of the present invention.

FIG. 3 is a side view showing another embodiment of the golf club shaft of the present invention.

FIG. 4 is a partial cross-sectional view along the axial direction of a shaft portion of the golf club shaft of the present invention.

FIG. 5 is a partial cross-sectional view along the axial direction of a shaft portion of the golf club shaft of the present invention.

FIG. 6 is a partial cross-sectional view along the axial direction of a shaft portion of the golf club shaft of the present invention.

FIG. 7 is a partial cross-sectional view of the shaft portion of the golf club shaft of the present invention along the axial direction.

FIG. 8 is a partial cross-sectional view along the axial direction of a shaft portion of the golf club shaft of the present invention.

FIG. 9 is a partial cross-sectional view along the axial direction of a shaft portion of the golf club shaft of the present invention.

FIG. 10 is a side view showing an example of a golf club shaft deviating from the present invention.

FIG. 11 is a side view showing another example of the golf club shaft deviating from the present invention.

FIG. 12 is a diagram showing a measurement result of a radius of curvature due to bending of a golf club shaft.

FIG. 13 is a view showing a measurement result of a bending rigidity of a golf club shaft.

[Explanation of symbols]

 1, 1 ', 1 "golf club shaft 2 tip 3 shaft 3A, 3B bulging 4 butt 11 base shaft 12A, 12B thick part P1, P2 bending point

Claims (7)

[Claims] 1. A shaft having a tip portion, a shaft portion, and a butt portion in order from one end along the axial direction of the shaft, wherein the shaft portion has two bulging portions along the axial direction, and A golf club shaft, characterized in that the golf club shaft has bending points in several places. 2. The method according to claim 1, further comprising a first flex point between the two bulges and a second flex point between the bulge and the butt. Golf club shaft. 3. The method according to claim 1, further comprising a first bending point between the tip portion and the bulging portion, and a second bending point between the two bulging portions. Golf club shaft. 4. The method according to claim 1, further comprising a first bending point between the tip portion and the bulging portion, and a second bending point between the other bulging portion and the butt portion. 1
2. The golf club shaft according to 1. 5. A method according to claim 1, further comprising a first bending point between the tip portion and the bulging portion, a second bending point between the bulging portion and a third bending point between the bulging portion and the butt portion. The golf club shaft according to claim 1 having a flex point. 6. The outer maximum diameter of the bulge at the local maximum point is within a range of 1.02 to 3.0 times the outer diameter of the shaft near the butt side of the bulge. The golf club shaft according to any one of claims 1 to 5. 7. The golf club shaft according to claim 1, wherein the length of one bulging portion in the axial direction occupies 5 to 40% of the length of the shaft portion. .