JPH09253255A - Fiber-reinforced resin-made shaft for golf club - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light shaft for a golf club which achieves a bending strength, a twisting property and a bending rigidity all with aimed characteristics required for the shaft for golf clubs satisfied and moreover, a stable quality. SOLUTION: A braid layer made up of braid yarns (a) and (a') and center yarn (b) to be braided into the braid yarns (a) and (a') is laminated in a plurality of layers. To achieve this, the braid yarns are braided at an angle of winding to the axis of the shaft in horizontal symmetry and the center yarn is braided into the braid yarns at an angle 0 deg. of winding to the axis of the shaft. In the braid layer composing the shaft, the number of individual yarns in the braid yarns (a) and (a') and the center yarn (b) is increased gradually from the inner layer to the outer layer to close up the interval of the yarns thereby minimizing the void (e).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fiber reinforced plastic golf club shaft, and more particularly to a fiber reinforced plastic golf club shaft formed into a braid by a knitting machine. .

[0002]

2. Description of the Related Art A shaft made of fiber reinforced plastic is
Since the weight is lighter than that of the metal shaft, there is an advantage that the head speed is increased during the swing and, as a result, the flight distance of the ball is increased. Further, as a method of manufacturing the fiber-reinforced plastic shaft, a sheet winding method and a filament winding method are generally used. In the sheet winding method, generally, reinforcing fibers are aligned and impregnated with a resin, and a prepreg-aligned aligned sheet is wound around a mandrel and then taped and heat-cured to be molded. The shaft manufactured by the sheet winding method, due to the manufacturing method, the winding start portion and the winding end portion of the prepreg sheet overlap with each other, or a step occurs due to non-overlap, or
Since a unidirectionally aligned sheet is cut into a trapezoidal shape and wrapped around it, the bending rigidity of the shaft does not become uniform in the circumferential direction due to the winding angle being different at the beginning and end of winding, and the quality is stable. It is hard to become a shaft. Further, since the shear elastic modulus is small, the shaft is easily twisted during a swing, it is difficult to control the direction of the face of the head, and it is difficult to carry the ball to a target location.

Further, the filament winding method is
In general, a resin-impregnated reinforcing fiber is helically wound around a mandrel to be covered therewith, followed by taping and heat-curing to be molded. The shaft manufactured by the filament winding method has uniform bending rigidity in the circumferential direction and less twist, but the manufacturing method requires that the reinforcing fibers be oriented in the 0 ° direction with respect to the axial direction of the shaft. Therefore, the bending rigidity becomes small, and sufficient bending strength cannot be obtained. Further, if the bending strength is to be satisfied, the amount of fibers wound around the mandrel must be increased, and the weight is increased, and the merit that the shaft made of fiber-reinforced plastic is lightweight and easy to swing cannot be realized.

In view of the above circumstances, therefore, in order to reduce the twist of the shaft, to make it lightweight and easy to swing, and to realize stable quality at the same time, as shown in FIG. In the process of forming a braid, the left and right braids a,
Inner surface of braid layer consisting of a'and left and right braids a, a '
A tubular body such as a golf shaft or a fishing rod in which a warp thread parallel to the axis of the tubular body is supplied to any one or both of the intermediate surfaces of the golf ball and a warp thread (hereinafter referred to as central thread b) layer is simultaneously formed at the time of forming the braid. Is known (see Japanese Patent Laid-Open No. 6-278216).

[0005]

However, in the golf shaft manufactured by the conventional method described above,
In the case of forming a braid with resin-impregnated yarn, the resin is impregnated after the braid is formed.In this case, the resin impregnation step after forming the braid or taping after the resin impregnation is performed. In the taping process for heat curing, the wound yarn is easily disturbed and meanders, so that the shaft performance as designed cannot be reproduced.

[0006] Usually, the fiber reinforced plastic golf shaft has a wall thickness of 1 mm even in the thinnest part in order to maintain strength.
Although the above is necessary, when it is attempted to obtain this thickness in one braid forming step as in the conventional method, the left and right braids a,
a ′ and the central yarn b, the number of monofilaments constituting each yarn must be increased to increase the thickness of each yarn.
The crossing portion c of a ′ or the crossing portion d in which the central yarn b is further added to the crossing portion of the left and right braids a and a ′ has a thickness of about 2 to 3 times, and a portion not intersecting with the crossing portion. Since the step difference is large, a large unevenness is formed on the surface of the shaft. Therefore, when manufacturing a golf shaft by forming a braid, it is necessary to form a braid layer with a thin yarn and to laminate the braid layers a plurality of times until the desired thickness is achieved.

If the braid layers are laminated as described above, the required fiber thickness can be secured, but as the braid layer becomes the outer layer of the shaft, the winding area thereof increases. Therefore, the void portion e formed between the left and right braided yarns a, a ′ and the central yarn b is formed to be larger as it becomes the outer layer of the shaft. When forming the braid layer on the mandrel, the tension applied to each yarn forming the braid layer by the knitting machine and acting in the longitudinal direction of the yarn, and the other yarn during braiding. If the yarn is preliminarily impregnated with the frictional resistance force generated by the contact, the frictional resistance force including the adhesion of the impregnated resin fixes the yarn at a desired position, but if the void portion e is large, that is, When the distances between the braided yarns a, a ′ and the central yarn b are not close to each other, the frictional resistance due to the contact with the yarns to be knitted can hardly be expected except at the intersecting portions, so that the yarns are mainly fixed to the yarns. It depends on the tensile tension applied in the longitudinal direction. Therefore,
Each yarn is strong against external force acting in the longitudinal direction but weak against external force acting on the yarn perpendicularly or at a certain angle, and the braid layer is formed by the yarn not previously impregnated with resin. After stacking, place it in a mold for molding, and put the shaft molding resin in the mold with high pressure such as RI (resin injection) method or RIM (reaction injection molding, reaction injection molding) method. When injected, there was a drawback in that the thread wound around the resin was disturbed and meandered.

Further, a braid layer is formed by threads impregnated with resin in advance, and after the braid layers are laminated, they are spirally wound with a heat-resistant wrapping tape such as polypropylene or polyester at a constant angle with respect to the shaft axis. After heating, the impregnated resin is melted and impregnated between the reinforcing fibers for curing and molding.If the yarn interval is not close, the tension of the taping causes the wound yarn to be disturbed and meander. Will end up. In this case, in particular, the central yarn is apt to be displaced in the direction in which the tape tension acts, and the strength as designed cannot be reproduced.

By the way, the winding angle of the braiding yarn can be freely adjusted by changing the rotation speed of the knitting machine and the mandrel transfer speed. Therefore, according to the above method, it is possible to increase the winding angle of the braiding yarn with respect to the shaft axis (0 degree) to make the yarn spacing closer as the outer layer portion of the shaft and the larger diameter portion of the shaft become larger. By using this method, the spacing between each yarn will be smaller and the yarn will not be disturbed.However, since the yarn spacing will be made closer by increasing the winding angle of the braiding yarn, the bending rigidity and bending strength of the shaft will be sufficient. Did not come to value. Therefore, in order to satisfy the bending rigidity and strength of the shaft, it is necessary to further increase the winding amount of the braid, and there are drawbacks that the shaft cannot be called a lightweight shaft and the shaft becomes heavy. Therefore, in view of the drawbacks found in the above-mentioned prior art, the present invention has a bending strength as a golf club shaft, a twist,
It is an object of the present invention to provide a lightweight golf club shaft that satisfies the desired characteristics in terms of bending rigidity and has stable quality.

[0010]

In order to achieve the above object, the present invention provides a braided yarn having a winding angle symmetrical with respect to a shaft axis and a central yarn having a winding angle of 0 ° with respect to the shaft axis. In a shaft for a fiber reinforced plastic golf club formed by a plurality of braid layers, the yarns constituting the braid layer are bundled into the number of yarns or the yarns from the inner layer to the outer layer. A shaft for a golf club made of fiber reinforced plastic having a structure in which the number of single fibers is gradually increased. The structure in which the number of yarns constituting the braid layer or the number of single fibers bundled in the yarn is sequentially increased from the inner layer to the outer layer depends on the design of characteristics such as bending rigidity and torsional rigidity of the shaft. The number of central yarns or the number of single fibers bundled in the central yarn may be sequentially increased, or the number of braids or the number of monofilaments bundled in the central yarn may be sequentially increased. it can.

The yarn used in the present invention includes inorganic fibers such as carbon fibers, glass fibers, alumina fibers and silicon carbide fibers, aramid fibers, organic fibers such as polyparaphenylene benzobisoxazole fibers, boron fibers, and the like.
It can be selectively used from a single or a mixture of metal fibers such as stainless fibers and titanium fibers, and the number of single fibers bundled in the yarn is 1000 to 2400.
You can use up to 0, but 1000 or 3000
It is more desirable to use one, 6000, or 12,000 because it is easy to wind. As the molding resin, epoxy resin,
Thermosetting resins such as unsaturated polyester resins, phenol resins, polyurethane resins, crosslinked epoxy modified polyaminoamide resins, polypropylene resins, polyphenylene sulfide resins, polyether ether ketone resins, polyether sulfone resins, ABS resins, nylon resins, etc. It can be selectively used from thermoplastic resins.

When the yarn is used in a state of being impregnated with resin in advance, the resin content of each yarn is 20% to 50% by volume regardless of whether the yarn is a braided yarn or a central yarn. %
It can be adjusted freely within the range. The shaft of the present invention has a weight of 35 to 60 g and a natural frequency of 190 to
210c. p. m. In the FRP shaft of No. 90 mm from the small diameter side of the shaft, this part is the most liable to break due to stress concentration when hitting the ball with a golf club, and the bending strength at this position is 120 kgf.
The above is 150 kgf or less. If the bending strength is 150 kgf or more, the rigidity of the shaft is adversely affected, the amount of reinforcing fibers increases, and the weight of the shaft increases, which is not preferable for the shaft of the present invention.

[0013]

A shaft for a fiber reinforced plastic golf club according to the present invention comprises a plurality of braided yarns having a winding angle symmetrical with respect to the shaft axis and a central yarn having a winding angle of 0 ° with respect to the shaft axis. Is a fiber reinforced plastic golf club shaft formed by the braid layer, each yarn constituting the braid layer, from the inner layer to the outer layer,
By gradually increasing the number of yarns or the number of monofilaments bundled in the yarns, the yarn intervals become closer, and the frictional resistance generated by the contact of each yarn can be increased. The yarn is not disturbed in the resin impregnation step after forming the object or in the taping step after resin impregnation.

Further, the number of yarns constituting the braid layer or the number of single fibers bundled in the yarns is gradually increased from the inner layer to the outer layer, and the shaft having particularly high bending rigidity and bending strength is formed. In such a case, the number of central yarns or the number of single fibers bundled in the central yarns is sequentially increased to make the yarn intervals denser,
It is possible to increase the frictional resistance force generated by the contact of each yarn, and the yarn will not be disturbed in the resin impregnation process after forming the braid or in the taping process after resin impregnation. Is obtained. In addition, each yarn constituting the braided layer is constituted by a fiber bundle of inorganic fibers, organic fibers and metal fibers, which are impregnated with resin in advance, or a fiber bundle of a mixed material. Since the adhesive force of the impregnated resin is added to the frictional resistance force generated by the contact between the yarns, it becomes easier to fix each yarn at a desired position as compared with the case where the braid is formed with the yarn not impregnated with the resin.

Further, by setting the resin content of each yarn constituting the braid layer to be 20% to 50% by volume, the performance as a fiber reinforced plastic shaft such as bending rigidity and torsional rigidity can be obtained. It can be fully demonstrated.
In this case, when the resin content of each yarn is less than 20% by volume, the amount of impregnated resin is insufficient with respect to the amount of reinforcing fibers, so that the shaft between the braided layer and the braided layer in the shaft after curing molding is insufficient. Therefore, delamination is likely to occur, which is not preferable. In addition, when the resin content of each yarn is greater than 50% by volume, the amount of impregnated resin is too much with respect to the amount of reinforcing fiber, so the flexural rigidity and torsional rigidity of the shaft after curing become very small. This is not preferable because it does not satisfy the performance required as a fiber reinforced plastic shaft. Although the weight, natural frequency, bending strength, etc. of the shaft of the present invention can be arbitrarily adjusted by design, the shaft has a weight of 35 to 60 g and a natural frequency of 190 to 210 c.
p. m. By setting the bending strength at a position 90 mm from the tip of the small diameter portion of the shaft to 120 kgf or more,
A shaft made of fiber-reinforced plastic that is lightweight, easy to swing, and strong against impact can be used.

[0016]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a front view of a shaft 1 according to the present embodiment,
FIG. 2 is an enlarged explanatory view showing the structure of the assembly of the shaft 1 of FIG. The shaft 1 of the present embodiment is, as shown in FIG.
Shaft axis 14 that is the central axis of the shaft 1 in the longitudinal direction
And the braided yarns a and a'which are knitted so as to have a bilaterally symmetrical winding angle, and the braided yarns a and a'which are knitted to have a winding angle of 0 ° with respect to the shaft axis. Central thread b
It has a structure formed by laminating a plurality of braid layers formed of (1) and (2). Then, the braid layer constituting the shaft 1 increases the number of each of the braid yarns a, a ′ and the central yarn b constituting the braid layer in order from the inner layer to the outer layer, thereby increasing the yarn interval. This is a shaft for a golf club made of fiber reinforced plastic, which is made dense and has a small void portion e.

Next, a method for manufacturing the fiber reinforced plastic golf club shaft according to this embodiment will be described. The mandrel used has a length of 1450 mm, a small-diameter side tip 4 mmφ, and a large-diameter side tip 14.75 mmφ. The yarn to be used is a roving yarn (UT500: made of a carbon fiber bundle impregnated with an epoxy resin in advance).
Nippon Oil Co., Ltd. product name). The number of single fibers bundled in the yarn is 6000, and the fineness of the fibers is 40.
The resin content is 0 g / km and the resin content is 25% by volume. The yarn is braided on the mandrel by a knitting machine. In this embodiment, as shown in FIG. 2, a braided yarn a having a winding angle symmetrical with respect to the shaft axis 14,
a ′ and a central yarn b having a winding angle of 0 ° with respect to the shaft axis are knitted in the same layer to form a braid layer, and a plurality of braid layers are laminated. The yarns constituting the braid layer were formed by sequentially increasing the numbers of the braid yarns a, a ′ and the central yarn b from the inner layer to the outer layer. The winding tension of the yarn at the time of braiding at this time is 1.0 kgf / mm ² . The number of windings of the braids a, a ′ and the central yarn b,
Table 1 shows the winding angles of the braids a and a ′ and the yarn intervals.

[0018]

[Table 1]

Here, regarding the meaning of ABCD described in the column of the winding angle of the braid, the winding angle in the range from the tip of the mandrel small diameter side to 250 mm is A2.
From the position of 50 mm to the further 680 mm ahead is bisected,
The small diameter side is B, the large diameter side is C, and the range from the 680 mm position to the large diameter side tip is D, and the winding angle is continuously changed in the range from A to D. . In the fiber reinforced plastic shaft intermediate after four braid layers are laminated according to the above-mentioned specifications, the intervals between the threads wound around the mandrel are closely adjacent to each other in each layer, and the void portion e is very small. It became a thing. The determination of the density of the yarn spacing is for determining visually the surface of each layer after braided formation completion, and the sparse when there are approximately 9 mm ² or more gap portion e.

Next, the fiber-reinforced plastic shaft intermediate was wound around with a heat-resistant wrapping tape, heat-cured, and then the mandrel was pulled out, and the wrapping tape was removed to obtain a fiber-reinforced plastic shaft molded product. The entire length of the fiber-reinforced plastic shaft molded product was trimmed, subjected to finish polishing, and painted to obtain a fiber-reinforced plastic shaft finished product.

A comparative example will be described below. COMPARATIVE EXAMPLE 1 AND COMPARATIVE EXAMPLE 2 The shafts of Comparative Examples 1 and 2 are each a set consisting of a braided yarn having a winding angle symmetrical with respect to the shaft axis and a central yarn having a winding angle of 0 ° with respect to the shaft axis. A fiber reinforced plastic golf club shaft having a structure formed by laminating a plurality of product layers, and having a structure in which the number of each thread in each braid layer is made equal in all layers. Next, a method for manufacturing a fiber reinforced plastic golf club shaft according to a comparative example will be described. The mandrel, the thread, and the winding tension of the thread used in Comparative Examples 1 and 2 are the same as those in the example. The number of windings of the braiding yarn and the central yarn, the winding angle of the braiding yarn, and the yarn interval are shown in Table 2 for Comparative Example 1 and Table 3 for Comparative Example 2. In addition, A-indicated in the column of winding angle of braid
The meaning of B-C-D and the method of determining the density of yarn intervals are the same as those in the embodiment.

[0022]

[Table 2]

[0023]

[Table 3]

Comparative Example 1 has the same specifications as the first layer of the embodiment (the number of windings of the braiding yarn and the central yarn, the winding angle of the braiding yarn), and is carried out until the same thickness as that of the embodiment is obtained. A braid was formed to the same weight as the example. Therefore,
The number of laminated layers is a five-layer structure, which is one layer larger than that of the embodiment. The intervals of the wound yarns are dense in the first layer, but sparse in the second and subsequent layers, and the voids are larger and larger toward the outer layer of the shaft, and are conspicuous in the ranges C and D. It was Comparative Example 2 has the same number of windings of the braided yarn and the central yarn as in the first layer of the embodiment, has the same thickness as the embodiment, has the same weight as the embodiment, and has a close yarn interval. In this way, the winding angle in the range from A to D is continuously changed for each layer to form a braid. Table 4 shows the total length, weight, diameter of the tip on the small diameter side, diameter of the tip on the large diameter side, yarn disorder, natural frequency, and bending strength of the finished fiber-reinforced plastic shaft.

[0025]

[Table 4]

Here, an outline of a method for measuring yarn disorder, natural frequency, and bending strength will be described. Regarding the disorder of the yarn, a writing line parallel to the shaft axis is previously inserted in the longitudinal direction of the mandrel, and at the same time as the shaft is formed, the resin that enters the writing line is cured and a convex is formed inside the shaft. When the finished shaft is cut at a pitch of 10 mm in the circumferential direction and the cross section is enlarged and observed,
An angle formed by the cross section of the yarn to be measured with respect to the center of the shaft is measured, and a change in this angle is regarded as a disorder of the yarn. For this example and Comparative Examples 1 and 2, briefly,
Only the central yarn was measured.

The natural frequency was measured by the natural frequency measuring device shown in FIG. The measuring method is as follows. First, the large-diameter portion side 2 of the shaft 1 is horizontally fixed by a fixing jig 4 attached to the arithmetic unit 15, and a predetermined weight jig 5 is fixed to the tip of the small-diameter portion side 3. . Time for the shaft 1 to block the infrared sensor between the light source 6 of the measuring unit 16 and the photoelectric cell 7 after pressing the weight jig 5 by hand to sink the shaft 1 for a certain distance and then releasing the hand to vibrate the shaft 1. Is measured
The number of vibrations per minute was converted by the counter unit 8 in the calculation unit 15 and displayed on the digital display panel 9 of the display unit for measurement. The distance L1 from the fixing jig 4 to the infrared sensor between the light source 6 and the photoelectric cell 7 is 680 m.
m, and the weight of the weight jig 5 is 287.5 g. In the present Example and Comparative Examples 1 and 2, as a guideline for the uniformity of the bending rigidity in the circumferential direction, that is, a guideline for the stability of quality, the first measured arbitrary longitudinal direction was set to 0 °, and the shaft axis was measured from there. Rotate 90 ° around and measure again, 0 °
The difference between the frequency in the direction and the frequency in the 90 ° direction is read.

Regarding bending strength, as shown in FIG.
The both ends in the length direction of the shaft test piece 10 cut to a predetermined size are placed on the support bases 13 and 13 ', and the central portion 11 of the shaft test piece 10 is applied by the pressure wedge 12 at a predetermined load speed.
The load is applied to and the breaking load is read. In addition,
The radius of the pressure wedge 12 is 75 mm, and the supporting bases 13 and 13 '
Has a radius of 12.5 mm and a load speed of 20 mm / min. Then, E, F shown in the column of bending strength in Table 4,
G and H represent bending strength measurement positions, E is a position 90 mm ahead from the tip of the shaft thin diameter portion 3 side, F is a position 175 mm ahead from the shaft thin diameter portion 3 end 3 and G is a shaft thin portion. A position 525 mm ahead from the tip of the side 3 and a symbol H means a position 175 mm ahead from the tip of the side 2 of the shaft large diameter portion. Also, the distance L between the fulcrums from the supporting bases 13 to 13 '
2 is 150 mm when the bending strength measurement position is E, F, G,
When H is 300 mm.

From Table 4, comparing Examples and Comparative Examples 1 and 2, the overall length, weight, diameter of the tip of the small diameter portion, and diameter of the tip of the large diameter portion are the same as designed. However, in Comparative Example 1, the yarn disorder was large, and the frequency in the 0 ° direction and 90 °
The difference in frequency in the direction is 5c. p. m. Therefore, the bending strength at each point from E to H was also weaker than that of the example. This is because the fiber reinforced plastic shaft intermediate body of Comparative Example 1 was not dense except for the first layer, and therefore the threads were displaced in the direction in which the tape tension acted at the time of taping, and were disturbed and meandered. Therefore, the shaft of Comparative Example 1
The fiber density was uneven, and voids where the resin was not completely filled became voids, and sufficient rigidity and strength could not be realized.

In Comparative Example 2, since the fiber interval between the fiber-reinforced plastic shaft intermediates was close, the yarns were not disturbed, and the natural frequencies in the 0 ° and 90 ° directions were also constant. However, compared with the embodiment, the natural frequency is 6c. p.
m. It was also small and the bending strength was weak. this is,
The fiber-reinforced plastic shaft intermediate of Comparative Example 2 is
Since the winding interval of the braid is increased by increasing the winding angle of the braid, that is, by increasing the winding amount of the braid, the flexural rigidity and the flexural strength of the finished shaft product are not sufficient. In contrast to the results of Comparative Examples 1 and 2, in the example, the number of the braided yarns and the central yarns is gradually increased from the inner layer to the outer layer to make the yarn spacing denser, so that the yarns are not disturbed and the 0 ° direction is obtained. And the natural frequency in the 90 ° direction is also constant,
And 197c. p. m. It was hard and the bending strength was sufficiently strong. It can be said that the shaft has sufficient flexural rigidity and flexural strength and is stable in quality even though it weighs 45 g.

[0031]

As described above, according to the present invention, a braid having a winding angle which is bilaterally symmetric with respect to the shaft axis and zero with respect to the shaft axis.
In a shaft for fiber reinforced plastic golf clubs, which is formed by a plurality of braid layers each having a central yarn having a winding angle of °, each yarn constituting the braid layer is formed from an inner layer to an outer layer. By gradually increasing the number of filaments or the number of monofilaments bundled in the filaments, the spacing between the filaments becomes smaller, and the frictional resistance generated by the contact of the filaments can be increased. In the resin impregnation step after forming the resin or in the taping step after resin impregnation, the yarn is not disturbed and meanders,
The degree of freedom in designing characteristics such as bending rigidity, bending strength, and torsional rigidity as a fiber-reinforced plastic shaft is improved.

Further, the number of central yarns or the number of monofilaments bundled in the yarns constituting the braided layer or the number of monofilaments bundled in the yarns is increased in order from the inner layer to the outer layer. By increasing the number of monofilaments that are present in sequence, the yarn spacing becomes closer, and the frictional resistance force caused by the contact of each yarn can be increased, and the resin impregnation process after forming the braid. In addition, in the taping process after resin impregnation, the yarn is not disturbed and meandered, and the weight is heavier than the shaft made of fiber reinforced plastic in which the winding amount of the braiding yarn is increased and the yarn interval is tight. Without increasing the bending rigidity and bending strength. The features of the present invention to be particularly emphasized are
In a shaft for a golf club to be formed into a braid, by increasing the number of each yarn constituting the braid layer or the number of monofilaments bundled in each yarn, the yarn interval is made closer, and as a golf club shaft. The point is that it is possible to provide a lightweight golf club shaft that satisfies the desired characteristics in terms of bending strength, twisting, and bending rigidity and has stable quality.

[Brief description of drawings]

FIG. 1 is a front view of a fiber reinforced plastic golf club shaft according to an embodiment of the present invention.

2 is an enlarged explanatory view showing the structure of the shaft assembly of FIG. 1. FIG.

FIG. 3 is an enlarged explanatory view showing a part of a braid layer after the second time of a golf club shaft formed into a braid by a conventional technique.

FIG. 4 is a top view of a natural frequency measuring device for a golf club shaft.

FIG. 5 is an explanatory diagram of a method for measuring bending strength of a golf club shaft.

[Explanation of symbols]

 1 Shaft 2 Large Diameter Side 3 Small Diameter Side 4 Fixing Fixture 5 Weight Fixture 6 Light Source 7 Photoelectric Cell 8 Counter Unit 9 Digital Display Panel 10 Shaft Test Specimen 11 Center Part 12 Pressing Wedge 13 Supporting Stand 13 'Supporting Stand 14 Shaft Axis 15 Calculation Part 16 Measuring Part a Braiding Thread a'Braiding Thread b Central Thread c Intersection d Intersection e Space Gap L1 Distance L2 Distance between fulcrums

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code Agency reference number FI Technical display location B29L 31:52

Claims (5)

[Claims] 1. A braid layer formed by laminating a plurality of braid layers each including a braid yarn having a winding angle symmetrical with respect to a shaft axis and a central yarn having a winding angle of 0 ° with respect to the shaft axis. In the shaft for fiber reinforced plastic golf club, each yarn constituting the braided layer is characterized in that the number of yarns or the number of monofilaments bundled in the yarns is sequentially increased from the inner layer to the outer layer. Fiber reinforced plastic golf club shafts. 2. The fiber according to claim 1, wherein, in the braid layer, the number of the central yarns or the number of single fibers bundled in the central yarn is sequentially increased from the inner layer to the outer layer. Reinforced plastic golf club shaft. 3. The yarns constituting the braided layer are made of fiber bundles of an inorganic fiber, an organic fiber and a metal fiber, which are impregnated with resin in advance, or a mixture of the fibers. A shaft for a golf club made of the fiber reinforced plastic according to 1 or 2. 4. The golf club made of fiber reinforced plastic according to claim 1, 2 or 3, wherein the resin content of each yarn constituting the braid layer is 20% to 50% by volume. Shaft for club. 5. The shaft has a weight of 35 to 60 g and a natural frequency of 190 to 210 c. p. m. ,
The fiber reinforced plastic golf club shaft according to claim 1, wherein the bending strength at a position 90 mm from the tip of the small diameter portion of the shaft is 120 kgf or more and 150 kgf or less.