JP3761652B2 - Golf club - Google Patents

Description

【０００７】
上記表１から、普及型はシャフト内側（つまりバイアス層）にはさほど大きな圧縮・引張応力が生じないが、オーバーホーゼル型の場合は、シャフト内側のバイアス層に大きな圧縮・引張応力が生じるということができ、このことからも、従来のオーバーホーゼル型のゴルフクラブがネック打ちやダフり打ちで破損し易いことが分かる。
【０００８】
そこで、本発明は、上述の問題を解決して、いわゆるネック打ちやダフり打ちに対して破損しにくく優れた耐久性を有するオーバーホーゼル型のゴルフクラブを提供することを目的とする。
【０００９】
【課題を解決するための手段】
上述の目的を達成するために本発明に係るゴルフクラブは、繊維強化樹脂製のシャフトが、強化繊維の配列方向がシャフトの軸心と平行な外層側のストレート層と、強化繊維の配列方向が上記軸心に対して所定角度傾斜した内層側のバイアス層とを、有し、該シャフトの先端部を、ヘッドに突設された中軸に外挿して接合するゴルフクラブであって、上記シャフトの先端部に於て上記バイアス層の内側でかつ最内層に、強化繊維の配列方向がシャフト軸心と平行なストレート層を、配設したものである。また、最内層に配設されたストレート層を、ヘッドの中軸の先端から上記シャフトの先端側へ１ cm 以上、かつ、上記中軸の先端から上記シャフトの基端側へ１cm以上の範囲にわたるように設けるのが好ましい。
【００１０】
【発明の実施の形態】
以下、図示の実施の形態に基き本発明を詳説する。
【００１１】
図１は本発明に係るゴルフクラブの実施の一形態を示し、１はヘッド、２は繊維強化樹脂製のシャフトである。このゴルフクラブは、ヘッド１にシャフト取付用の中軸３が突設され、シャフト２の先端部をその中軸３に外挿して接合したいわゆるオーバーホーゼル型のゴルフクラブである。
【００１２】
しかして、図２に示すように、シャフト２は、強化繊維の配列方向がシャフト軸心Ｌと平行な最外層を成すストレート層４ａ及びその内側のストレート層４ｂと、ストレート層４ｂの内側に積層されると共に強化繊維の配列方向がシャフト軸心Ｌに対して所定角度傾斜したバイアス層５ａ及びその内側のバイアス層５ｂと、バイアス層５ｂの内側であって先端部のみに積層されると共に強化繊維の配列方向がシャフト軸心Ｌと平行な最内層を成すストレート層６と、から成る。
【００１３】
つまり、シャフト２の先端部の最内層に、強化繊維の配列方向がシャフト軸心Ｌと平行なストレート層６を、配設する。かつ、ストレート層６を、シャフト２の先端から所定寸法Ｑだけ基端側に入った位置に配置する。さらに、ストレート層６は、ヘッド１の中軸３の先端３ａからシャフト軸心Ｌと平行な方向に±１cm以上の範囲にわたるように設けられる。従って、ストレート層６の長さ寸法Ｎは、２cm以上に設定される。ここで、中軸３の先端３ａからシャフト２の先端側へ向いた方向を＋（プラス）とし、中軸３の先端３ａからシャフト２の基端側へ向いた方向を−（マイナス）とする。
【００１４】
また、ストレート層４ａ，４ｂ、バイアス層５ａ，５ｂ、及び、ストレート層６は、炭素繊維やガラス繊維等の強化繊維を夫々の方向に配設し、エポキシ樹脂等の熱硬化性樹脂を含浸させてプリプレグを形成し、このプリプレグを加熱硬化させた繊維強化樹脂である。
【００１５】
即ち、図３に示すように、各層のプリプレグを形成し、このプリプレグを、テーパ状のマンドレル７に巻設する。具体的には、マンドレル７の先端部に、最内層のストレート層６に対応するプリプレグ12を巻き、その後、バイアス層５ｂ, ５ａに対応するプリプレグ13ｂ，13ａ、ストレート層４ｂ, ４ａに対応するプリプレグ14ｂ，14ａの順に巻き付ける。次に、テーピング、焼成処理をして、マンドレル７の脱去、テープ剥離等を行えば、シャフト２が完成する。さらに、そのシャフト２をヘッド１の中軸３に外挿させれば、本発明のゴルフクラブが完成する（図１と図２参照）。
【００１６】
なお、図３に於て、ストレート層４ａ，４ｂのプリプレグ14ａ，14ｂの水平な複数の平行線と、バイアス層５ａ，５ｂのプリプレグ13ａ，13ｂの複数の斜線は、強化繊維の方向を示す。この場合、プリプレグ13ａ（バイアス層５ａ）の強化繊維の傾斜角度θは＋45°であり、プリプレグ13ｂ（バイアス層５ｂ）の強化繊維の傾斜角度θは−45°である。また、ストレート層４ａ，４ｂのプリプレグ14ａ，14ｂと、バイアス層５ａ，５ｂのプリプレグ13ａ，13ｂの長さ寸法は、互いに同一であり、最内層のストレート層６のプリプレグ12の長さ寸法はシャフトの全長に比してきわめて短く設定される。
【００１７】
しかして、（図１と図２にもどって）このゴルフクラブを使用して、ボールをヘッド１のネック部（中軸３近傍部）で打った場合（いわゆるネック打ち）、あるいは、地面を直接叩いた場合（いわゆるダフり打ち）等、ヘッド１に大きな外力が作用すると、それにより生じる曲げモーメントは、ヘッド１の中軸３からストレート層６に伝わり、ストレート層６にシャフト軸心Ｌと同方向の引張応力と圧縮応力が生じる。そして、ストレート層６の補強繊維の方向はシャフト軸心Ｌと平行であるため、補強繊維の方向とこれらの応力の方向が同一となり、大きな強度が得られる。従って、ストレート層６は、ネック打ちやダフリ打ち等による曲げモーメントに十分に耐える。
【００１８】
ところで、ネック打ちやダフリ打ちによりシャフト２に作用するモーメントは、ねじりモーメントよりも曲げモーメントの方が大きいことが、明らかとなっている。しかして、ストレート層４ａ，４ｂは最外層にあるため、そのストレート層４ａ，４ｂを内層側に配した場合よりもシャフト２全体の曲げ剛性及び曲げ強度が大きくなり、大きな曲げモーメントに十分に耐え得る。さらに、ストレート層４ａ，４ｂの内側のバイアス層５ａ，５ｂにより、十分なねじり剛性及びねじり強度が得られる。
【００１９】
従って、このゴルフクラブによれば、ネック打ちやダフリ打ちに耐え得る十分大きな強度を実現できる。言い換えれば、ネック打ちやダフリ打ちをしても、シャフト２が破損する危険性が大幅に減少する。かつ、打撃の際に受ける曲げモーメントとねじりモーメントに効果的に対応でき、優れた打球特性が得られる。しかも、シャフト２の必要な箇所───即ちシャフト２のヘッド１の中軸３の先端３ａ近傍部───のみを効率的に補強できる。かつ、ストレート層６の材料を節約できる。なお、ストレート層６を、ヘッド１の中軸３の先端３ａからシャフト軸心Ｌと平行な方向に±１cm以上の範囲にわたるように設けたのは、±１cm未満では、ストレート層６が短いため、ネック打ちやダフリ打ちによりバイアス層５ａ，５ｂに生じるシャフト軸心Ｌと同方向の引張応力と圧縮応力が局部的に大きくなり───即ち応力集中が生じて───破損し易くなってしまうからである。
【００２０】
次に、図４は、本発明に係るゴルフクラブの他の実施の形態を示し、シャフト２のストレート層６の基端部に段差部16が形成される。かつ、ストレート層６は、ヘッド１の中軸３の先端３ａからシャフト軸心Ｌと平行な方向に±１cm以上の範囲にわたるように設けられる。
【００２１】
また、シャフト２は、図５に示すように、先端寄りに段付部８を有し、かつ、その段付部８よりも先端側が小径部９とされ、基端側が大径のテーパ部10とされたマンドレル７を使用して形成される。
【００２２】
具体的には、マンドレル７の小径部９に、最内層のストレート層６に対応するプリプレグ12を、テーパ部10と段差が無くなるまで巻き、その後、バイアス層５ｂ, ５ａに対応するプリプレグ13ｂ，13ａ、ストレート層４ｂ, ４ａに対応するプリプレグ14ｂ，14ａの順に巻き付ける。次に、テーピング、焼成処理をして、マンドレル７の脱去、テープ剥離等を行う。なお、バイアス層５ａの強化繊維の傾斜角度θは＋45°であり、その内側のバイアス層５ｂの強化繊維の傾斜角度θは−45°である。
【００２３】
このように構成したことにより、シャフト２のストレート層６の上にバイアス層５ａ，５ｂとストレート層４ａ, ４ｂを巻き付けるにもかかわらず、そのバイアス層５ａ，５ｂとストレート層４ａ, ４ｂが弯曲することは無い。従って、応力集中を防止でき、シャフト２の強度が一層大きくなる。
【００２４】
なお、本発明のゴフルクラブに於て、シャフト２のバイアス層５ａ，５ｂの強化繊維の傾斜角度θは±45°以外にも、±10°〜±80°程度の範囲内で変更自由である。これは、傾斜角度θが±10°未満では、シャフト２全体のねじり剛性及びねじり強度が小さくなり過ぎるためであり、傾斜角度θが±80°を越えると、バイアス層５ａ，５ｂの曲げ剛性及び曲げ強度が極端に小さくなるからである。また、図例ではヘッド１はアイアンヘッドであるが、ウッド型ヘッドとするも好ましい。
【００２５】
【実施例】
以下、実施例を示す。
炭素繊維を相互に平行かつシート状に揃えてエポキシ樹脂を含浸して成る一方向性のプリプレグを、表２にしたがって形成した後、各層のプリプレグをマンドレル７に巻設し、その後はテーピング、焼成処理をして、マンドレル７の脱去、テープ剥離等を行い、本発明の実施例に対応するオーバーホーゼル型シャフト２（図１〜図３参照）と、従来構造をもつ従来例のオーバーホーゼル型シャフト（図６参照）を形成した。
【００２６】
【表２】

【００２７】
これらのシャフトに、ネック部の形状以外が全て相互に同一とされたヘッド（３番アイアンのヘッド）を取付けて実施例のゴルフクラブと従来例のゴルフクラブを作製した。なお、従来例は、最内層にストレート層を有していない点に於いて実施例と異なる。
【００２８】
次に、スイングロボットによりダフり打ちを行った。その際、ヘッドスピードが40ｍ／ｓとなるように設定し、かつ、ヘッドが最下点から10cm手前のところでマット面に当たるように設定した。なお、マット面は、一般的な練習場と同様に、コンクリート面上に人工芝マットを敷いて形成した。そして、実施例と従来例のゴルフクラブを夫々 100回ずつダフり打ちした。その結果を次の表３に示す。
【００２９】
【表３】

【００３０】
上記表３から明らかなように、従来例のゴルフクラブでは、37回目のダフり打ちにより、シャフト先端内側に亀裂が生じ、かつ、ヘッドがぐらついた。これに対し、実施例のゴルフクラブは、 100回のダフり打ちに耐えた。これにより、実施例のゴルフクラブ（シャフト）は、従来例よりも強度が大きく、耐久性に優れている。
【００３１】
【発明の効果】
本発明は上述の構成により、次のような著大な効果を奏する。
【００３２】
請求項１記載のゴルフクラブによれば、シャフト２を繊維強化樹脂製とし、かつ、シャフト２の先端部をヘッド１の中軸３に外挿したオーバーホーゼル型のゴルフクラブとしても、ネック打ちやダフリ打ちに耐え得る十分大きな強度を実現できる。従って、ネック打ちやダフリ打ちをしても、シャフト２が破損する危険性が大幅に減少する。
【００３３】
請求項２記載のゴルフクラブによれば、請求項１記載のものと同様の効果を奏すると共に、ネック打ちやダフリ打ちに対するシャフト２の破損の危険性を有効に防止できる。
【図面の簡単な説明】
【図１】本発明の実施の一形態を示す要部正面図である。
【図２】要部拡大断面図である。
【図３】シャフト製造方法説明図である。
【図４】本発明の他の実施の形態の要部拡大断面図である。
【図５】他のシャフト製造方法説明図である。
【図６】従来例のシャフト製造方法説明図である。
【符号の説明】
１ ヘッド
２ シャフト
３ 中軸
３ａ 先端
４ａ ストレート層
５ｂ バイアス層
６ ストレート層
Ｌ シャフト軸心[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a golf club.
[0002]
[Prior art]
Conventionally, in a golf club having a shaft made of fiber reinforced resin such as FRP, a plurality of bias layers in which reinforcing fibers of fiber reinforced resin are arranged inclined with respect to the shaft axis are arranged, and the reinforcing fibers are outside of the shaft. In general, a plurality of straight layers arranged in parallel to the longitudinal direction are arranged. The reason is that the bias layer obtains an appropriate torsional rigidity with respect to the torsional moment generated in the shaft at the time of impact with the ball (acting in the circumferential direction of the shaft), and the straight layer has the bending moment generated in the shaft (in the shaft). This is to obtain an appropriate bending rigidity. Also, the reason for placing the straight layer outside the bias layer is that the torsional moment and bending moment are both greater than the inside of the shaft, but the bending moment is greater than the torsional moment, so the bending stiffness is effectively increased. This is because it is necessary to arrange the straight layer on the outside in order to improve.
[0003]
In a golf club of a type in which a shaft in which a straight layer of fiber reinforced resin is arranged outside a bias layer is inserted into an insertion hole provided in a neck portion of the head (hereinafter also referred to as a popular type), the head The bending and torsional moment generated in is first transmitted to the straight layer outside the shaft. The bending moment is larger than the torsional moment, and the straight layer can sufficiently cope with the bending moment, so there is no problem.
[0004]
[Problems to be solved by the invention]
However, in a golf club of a type (hereinafter sometimes referred to as an overhosel type) in which a tip end portion of a shaft in which a straight layer is arranged outside a bias layer is extrapolated to a central shaft protruding from the head The generated bending moment is first transmitted to the bias layer. For this reason, if the player strikes the ball with the neck of the head (so-called neck strike) or directly strikes the ground (so-called duffle strike) and a large external force acts on the club, the inner bias layer will withstand the bending moment. There were times when it was destroyed.
[0005]
By the way, it is difficult to prove by experiments that an overhosel type golf club applies a large force to the inner bias layer when necking or duffing. This is because it is impossible to put a strain gauge inside the shaft. Therefore, the inventors analyzed this using FEM (finite element method). As analysis conditions, the same shaft and head (No. 1 wood) are used, and only the method of joining the shaft and the head is used, with the popular type in which the shaft is inserted into the insertion hole of the head and the shaft on the center shaft protruding from the head. The neck was struck with the head speed of 45 m / s. The analysis results were as shown in Table 1 below.
[0006]
[Table 1]

[0007]
From Table 1 above, the popular type does not generate much compressive / tensile stress inside the shaft (that is, the bias layer), but in the case of the over-hosel type, large compressive / tensile stress occurs in the bias layer inside the shaft. From this, it can be seen that the conventional over-hosel type golf club is easily damaged by necking or duffing.
[0008]
Accordingly, an object of the present invention is to solve the above-described problems and to provide an overhosel type golf club that is not easily damaged by so-called necking and duffing and has excellent durability.
[0009]
[Means for Solving the Problems]
In order to achieve the above-described object, a golf club according to the present invention includes a shaft made of fiber reinforced resin, a straight layer on the outer layer side in which the arrangement direction of the reinforcement fibers is parallel to the axis of the shaft, and the arrangement direction of the reinforcement fibers. A golf club having an inner layer-side bias layer inclined at a predetermined angle with respect to the shaft center, the tip portion of the shaft being externally joined to a central shaft protruding from the head, A straight layer in which the reinforcing fibers are arranged in parallel to the shaft axis is disposed inside the bias layer and in the innermost layer at the tip. In addition, the straight layer disposed in the innermost layer extends over a range of 1 cm or more from the tip of the center axis of the head to the tip side of the shaft and 1 cm or more from the tip of the center axis to the base end side of the shaft. It is preferable to provide it.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
The present invention will be described in detail below based on the illustrated embodiment.
[0011]
FIG. 1 shows an embodiment of a golf club according to the present invention, wherein 1 is a head, and 2 is a shaft made of fiber reinforced resin. This golf club is a so-called over-hosel type golf club in which a shaft 1 is attached to a head 1 and a shaft 2 is projected from the head 1, and a tip portion of a shaft 2 is externally joined to the shaft 3.
[0012]
As shown in FIG. 2, the shaft 2 is laminated on the inner side of the straight layer 4a and the straight layer 4b that forms the outermost layer in which the reinforcing fiber is arranged in parallel with the shaft axis L and the straight layer 4b. The bias fiber 5a and the bias layer 5b on the inner side of the bias layer 5a, and the inner side of the bias layer 5b, and the reinforcing fiber are laminated only on the front end portion and the reinforcing fiber The straight layer 6 forms an innermost layer whose arrangement direction is parallel to the shaft axis L.
[0013]
That is, the straight layer 6 in which the reinforcing fibers are arranged in parallel with the shaft axis L is disposed in the innermost layer at the tip of the shaft 2. And the straight layer 6 is arrange | positioned in the position which entered the base end side by the predetermined dimension Q from the front-end | tip of the shaft 2. FIG. Further, the straight layer 6 is provided so as to cover a range of ± 1 cm or more in the direction parallel to the shaft axis L from the tip 3 a of the central shaft 3 of the head 1. Therefore, the length dimension N of the straight layer 6 is set to 2 cm or more. Here, the direction from the distal end 3a of the intermediate shaft 3 toward the distal end side of the shaft 2 is defined as + (plus), and the direction from the distal end 3a of the intermediate shaft 3 toward the proximal end side of the shaft 2 is defined as − (minus).
[0014]
The straight layers 4a and 4b, the bias layers 5a and 5b, and the straight layer 6 are provided with reinforcing fibers such as carbon fibers and glass fibers in respective directions and impregnated with a thermosetting resin such as an epoxy resin. This is a fiber reinforced resin obtained by forming a prepreg and heat-curing the prepreg.
[0015]
That is, as shown in FIG. 3, a prepreg of each layer is formed, and this prepreg is wound around a tapered mandrel 7. Specifically, the prepreg 12 corresponding to the innermost straight layer 6 is wound around the tip of the mandrel 7, and then the prepregs 13b and 13a corresponding to the bias layers 5b and 5a and the prepreg corresponding to the straight layers 4b and 4a are wound. Wind in the order of 14b, 14a. Next, if taping and baking are performed and the mandrel 7 is removed and the tape is peeled off, the shaft 2 is completed. Further, when the shaft 2 is extrapolated to the center shaft 3 of the head 1, the golf club of the present invention is completed (see FIGS. 1 and 2).
[0016]
In FIG. 3, a plurality of horizontal parallel lines of the prepregs 14a and 14b of the straight layers 4a and 4b and a plurality of oblique lines of the prepregs 13a and 13b of the bias layers 5a and 5b indicate the directions of the reinforcing fibers. In this case, the inclination angle θ of the reinforcing fibers of the prepreg 13a (bias layer 5a) is + 45 °, and the inclination angle θ of the reinforcing fibers of the prepreg 13b (bias layer 5b) is −45 °. Also, the length dimensions of the prepregs 14a and 14b of the straight layers 4a and 4b and the prepregs 13a and 13b of the bias layers 5a and 5b are the same, and the length dimension of the prepreg 12 of the innermost straight layer 6 is the shaft. It is set to be extremely short compared to the total length of.
[0017]
Thus, (going back to FIGS. 1 and 2), when this golf club is used, the ball is hit at the neck portion of the head 1 (the vicinity of the central shaft 3) (so-called neck hitting), or directly hits the ground. When a large external force is applied to the head 1 such as in the case of so-called duffing, the bending moment generated thereby is transmitted from the central shaft 3 of the head 1 to the straight layer 6, and is transmitted to the straight layer 6 in the same direction as the shaft axis L. Tensile stress and compressive stress are generated. And since the direction of the reinforcing fiber of the straight layer 6 is parallel to the shaft axis L, the direction of the reinforcing fiber and the direction of these stresses are the same, and a large strength is obtained. Accordingly, the straight layer 6 sufficiently withstands a bending moment caused by necking or duffing.
[0018]
By the way, it is clear that the moment acting on the shaft 2 due to necking or duffing is larger in bending moment than torsional moment. Since the straight layers 4a and 4b are in the outermost layer, the bending rigidity and bending strength of the shaft 2 as a whole are larger than when the straight layers 4a and 4b are arranged on the inner layer side, and sufficiently withstand a large bending moment. obtain. Furthermore, sufficient torsional rigidity and torsional strength can be obtained by the bias layers 5a and 5b inside the straight layers 4a and 4b.
[0019]
Therefore, according to this golf club, it is possible to realize a sufficiently large strength that can withstand neck hitting and duff hitting. In other words, the risk of damaging the shaft 2 is greatly reduced even when the neck is hit or duffled. In addition, it can effectively cope with the bending moment and torsional moment that are received at the time of hitting, and excellent hitting characteristics can be obtained. In addition, it is possible to efficiently reinforce only the necessary portion of the shaft 2, that is, the vicinity of the tip 3a of the central shaft 3 of the head 1 of the shaft 2. And the material of the straight layer 6 can be saved. The straight layer 6 is provided so as to extend in a range of ± 1 cm or more in the direction parallel to the shaft axis L from the tip 3a of the central shaft 3 of the head 1 because the straight layer 6 is short at less than ± 1 cm. Tensile stress and compressive stress in the same direction as the shaft axis L generated in the bias layers 5a and 5b due to necking or duffing are locally increased-that is, stress concentration occurs-and easily breaks. Because.
[0020]
Next, FIG. 4 shows another embodiment of the golf club according to the present invention, and a stepped portion 16 is formed at the base end portion of the straight layer 6 of the shaft 2. Further, the straight layer 6 is provided so as to cover a range of ± 1 cm or more in the direction parallel to the shaft axis L from the tip 3 a of the central shaft 3 of the head 1.
[0021]
Further, as shown in FIG. 5, the shaft 2 has a stepped portion 8 closer to the tip, and the tip end side of the stepped portion 8 is a small diameter portion 9 and the proximal end side is a tapered portion 10 having a large diameter. The mandrel 7 is formed.
[0022]
Specifically, the prepreg 12 corresponding to the innermost straight layer 6 is wound around the small diameter portion 9 of the mandrel 7 until there is no step difference from the taper portion 10, and then the prepregs 13b and 13a corresponding to the bias layers 5b and 5a are wound. The prepregs 14b and 14a corresponding to the straight layers 4b and 4a are wound in this order. Next, taping and baking are performed to remove the mandrel 7 and peel the tape. The inclination angle θ of the reinforcing fibers of the bias layer 5a is + 45 °, and the inclination angle θ of the reinforcing fibers of the bias layer 5b on the inside is −45 °.
[0023]
With this configuration, the bias layers 5a and 5b and the straight layers 4a and 4b are bent despite the bias layers 5a and 5b and the straight layers 4a and 4b being wound around the straight layer 6 of the shaft 2. There is nothing. Therefore, stress concentration can be prevented and the strength of the shaft 2 is further increased.
[0024]
In the gouffle club of the present invention, the inclination angle θ of the reinforcing fibers of the bias layers 5a and 5b of the shaft 2 can be changed within a range of about ± 10 ° to ± 80 ° in addition to ± 45 °. This is because if the inclination angle θ is less than ± 10 °, the torsional rigidity and torsional strength of the entire shaft 2 become too small. If the inclination angle θ exceeds ± 80 °, the bending rigidity and the bias layers 5a and 5b This is because the bending strength becomes extremely small. In the illustrated example, the head 1 is an iron head, but a wood-type head is also preferable.
[0025]
【Example】
Examples are shown below.
A unidirectional prepreg formed by impregnating an epoxy resin with carbon fibers aligned in parallel and in sheet form is formed according to Table 2, and then the prepreg of each layer is wound around a mandrel 7 and then taping and firing. After processing, the mandrel 7 is removed, the tape is peeled off, etc., and the overhosel type shaft 2 (see FIGS. 1 to 3) corresponding to the embodiment of the present invention and the overhosel type of the conventional example having the conventional structure A shaft (see FIG. 6) was formed.
[0026]
[Table 2]

[0027]
A head (3 iron head) having the same shape except for the shape of the neck portion was attached to these shafts to produce the golf club of the example and the golf club of the conventional example. The conventional example differs from the example in that the innermost layer does not have a straight layer.
[0028]
Next, duffing was performed with a swing robot. At that time, the head speed was set to 40 m / s, and the head was set to hit the mat surface 10 cm before the lowest point. The mat surface was formed by laying an artificial turf mat on the concrete surface in the same manner as a general practice field. Then, the golf clubs of the example and the conventional example were each duffed 100 times. The results are shown in Table 3 below.
[0029]
[Table 3]

[0030]
As is apparent from Table 3 above, in the golf club of the conventional example, the 37th duffing caused a crack in the shaft tip inner side and the head wobbled. On the other hand, the golf club of the example endured 100 times of duffing. As a result, the golf club (shaft) of the example is stronger than the conventional example and has excellent durability.
[0031]
【The invention's effect】
The present invention has the following remarkable effects by the above-described configuration.
[0032]
According to the golf club of the first aspect, even when the shaft 2 is made of fiber reinforced resin and the tip portion of the shaft 2 is extrapolated to the center shaft 3 of the head 1, A sufficiently large strength that can withstand hitting can be realized. Therefore, the risk of the shaft 2 being damaged is greatly reduced even when the neck is hit or duffled.
[0033]
According to the golf club of the second aspect, the same effect as that of the first aspect can be obtained, and the risk of the shaft 2 being damaged due to necking or duffing can be effectively prevented.
[Brief description of the drawings]
FIG. 1 is a front view of an essential part showing an embodiment of the present invention.
FIG. 2 is an enlarged cross-sectional view of a main part.
FIG. 3 is an explanatory view of a shaft manufacturing method.
FIG. 4 is an enlarged cross-sectional view of a main part of another embodiment of the present invention.
FIG. 5 is an explanatory view of another shaft manufacturing method.
FIG. 6 is an explanatory diagram of a conventional shaft manufacturing method.
[Explanation of symbols]
1 Head 2 Shaft 3 Middle shaft 3a Tip
4a straight layer
5b Bias layer 6 Straight layer L Shaft axis

Claims (2)

The shaft (2) made of fiber reinforced resin has a straight layer (4a) on the outer layer side in which the arrangement direction of the reinforcing fibers is parallel to the axis (L) of the shaft (2), and the arrangement direction of the reinforcing fibers is the axis ( L) and a bias layer (5b) on the inner layer side inclined at a predetermined angle with respect to L), and the tip of the shaft (2) is extrapolated to a central shaft (3) projecting from the head (1). A golf club to be joined, wherein a straight layer in which the reinforcing fibers are arranged in parallel to the shaft axis (L) is located at the inner end of the bias layer (5b) at the tip of the shaft (2). A golf club characterized in that (6) is disposed. The straight layer (6) disposed in the innermost layer is at least 1 cm from the tip (3a) of the center shaft (3) of the head (1) to the tip side of the shaft (2), and the straight shaft (3) The golf club according to claim 1, wherein the golf club is provided so as to cover a range of 1 cm or more from the distal end (3 a) to the proximal end side of the shaft (2) .

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