CN114653031A

CN114653031A - Method for manufacturing shaft for golf club, and golf club provided with same

Info

Publication number: CN114653031A
Application number: CN202111181131.0A
Authority: CN
Inventors: 户谷祯志
Original assignee: Globeride Inc
Current assignee: Globeride Inc
Priority date: 2019-12-27
Filing date: 2021-10-11
Publication date: 2022-06-24
Also published as: CN113041583A; CN113041583B; JP7438927B2; JP2021106874A

Abstract

The invention provides a method for manufacturing a shaft for a golf club, a golf club shaft and a golf club with the shaft, wherein the downward deflection of the club head near an impact point is reduced, so that the force is more concentrated in a hitting direction to improve the club head speed. Specifically, the method for manufacturing a hollow shaft for a golf club comprises at least 3 axial prepreg sheets in which reinforcing fibers are aligned along the axial direction over the entire length of the shaft in the axial direction, wherein the winding start position and the winding end position of the axial prepreg sheets coincide or partially overlap with each other in the circumferential direction of the shaft, and the winding start position and the winding end position of the axial prepreg sheets are either a position greater than 90 degrees and less than 270 degrees in the circumferential direction from a reference position of the shaft or a position less than 90 degrees or greater than 270 degrees in the circumferential direction from the reference position of the shaft.

Description

Method for manufacturing shaft for golf club, and golf club provided with same

Technical Field

The present invention relates to a method of manufacturing a shaft for a golf club, and a golf club provided with the shaft.

Background

Conventionally, there has been proposed a golf club technique including a shaft for a golf club in consideration of deflection of the shaft at the time of a swing. For example, japanese patent application laid-open No. 2000-93568 (patent document 1) discloses a shaft which is a golf club shaft obtained by laminating prepreg sheets made of fiber-reinforced resin such as carbon fiber and curing the prepreg sheets, and which is lightweight and has sufficient strength in practical use.

Further, a golf club shaft technique which is light in weight, has high rigidity and elasticity, and has good directivity of hitting a ball has been proposed. For example, japanese patent application laid-open No. 2000-317022 (patent document 2) discloses a fiber-reinforced hollow golf club shaft in which a flat surface is formed along the longitudinal direction in at least a part of the inner wall surface of a hollow portion in the direction orthogonal to the longitudinal direction of the shaft.

Patent document

Patent document 1: japanese laid-open patent publication No. 2000-93568

Patent document 2: japanese patent laid-open No. 2000-317022

Disclosure of Invention

However, in the golf club body shown in patent document 1, weight reduction and strength improvement are considered, but there is a problem that it is difficult to sufficiently transmit force to a shot due to downward (toe down) deflection of the head in the vicinity of the impact point. On the other hand, in the golf club disclosed in patent document 2, even if a lightweight and highly elastic golf club shaft can be provided, there is a problem that it is difficult to avoid downward deflection of the head in the vicinity of the impact point, and it is difficult to sufficiently transmit the force to the shot, as in patent document 1. Here, the downward direction of the head means a direction in which the head is pulled toward the player side when the head center of the head is aligned with the center of the placed golf ball and the head center of the head moves inward with respect to the center of the golf ball due to the centrifugal force and the gravity applied to the head when the golf club is swung next, and the downward amount of the head means the amount of movement of the head.

An object of an embodiment of the present invention is to provide a method of manufacturing a shaft for a golf club, and a golf club provided with the shaft, which can improve a head speed by reducing downward deflection of a head near an impact point and concentrating a force in a hitting direction. Other objects of embodiments of the present invention will become apparent by reference to the specification as a whole.

In order to achieve the above object, a first aspect of the present invention is a method for manufacturing a shaft for a hollow golf club, the method comprising winding and laminating a plurality of prepreg sheets in which a synthetic resin is impregnated into reinforcing fibers on a mandrel and then performing a heat treatment,

the plurality of prepreg sheets includes at least 3 axial prepreg sheets in which reinforcing fibers are aligned along the axial direction of the shaft over the entire length in the axial direction,

at least 3 pieces of the axial prepreg sheets, each of which has a winding start position coinciding with or partially overlapping a winding end position in a circumferential direction of the shaft,

each of the winding start position and the winding end position of at least 3 pieces of the axial prepreg sheets is either a position greater than 90 degrees and less than 270 degrees in the circumferential direction from a reference position of the shaft or a position less than 90 degrees or greater than 270 degrees in the circumferential direction from the reference position of the shaft.

In one embodiment of the first invention, the winding start position and the winding end position of at least 3 pieces of the axial prepreg sheets overlap each other by 0 to 3 mm.

In another embodiment, the winding start position and the winding end position of at least 3 pieces of the axial prepreg sheets are 135 degrees, 180 degrees, and 225 degrees from the reference position, respectively.

In another embodiment, the winding start position and the winding end position of at least 3 pieces of the axial prepreg sheets are at positions of 225 degrees, 135 degrees, and 180 degrees from the reference position, respectively, and the winding is performed in this order.

In another embodiment, the winding start position and the winding end position of at least 3 pieces of the axial prepreg sheets are positions 315 degrees, 0 degrees, and 45 degrees from the reference position, respectively.

In another embodiment, the winding start position and the winding end position of at least 3 pieces of axial prepreg sheets are at positions of 45 degrees, 315 degrees, and 0 degrees from the reference position, respectively, and the winding is performed in this order.

In another embodiment, the winding start position and the winding end position of at least 3 pieces of the axial prepreg sheets are both 180 degrees from the reference position.

In another embodiment, the winding start position and the winding end position of at least 3 pieces of the axial prepreg sheets are both 0 degrees from the reference position.

In another embodiment, the reference position is a position opposite to a position in a downward direction of the head on a cross section of the shaft perpendicular to the longitudinal direction.

In another embodiment, the unidirectional prepreg further includes prepreg sheets in which the reinforcing fibers are aligned in an oblique direction or a perpendicular direction with respect to the axial direction of the shaft in at least 3 layers inside the unidirectional prepreg sheets.

In another embodiment, the shaft further includes a prepreg sheet as an inner reinforcing layer and/or an outer reinforcing layer in an innermost layer and/or an outermost layer of the tip end portion of the shaft.

A second aspect of the present invention is a shaft for a golf club manufactured by any of the above-described methods, including at least 3 reinforcing fiber layers in which fiber directions are aligned in an axial direction over an entire length of the shaft in the axial direction.

A third aspect of the present invention is a golf club including the above-described shaft for a golf club and a golf club head attached to a tip end of the shaft for a golf club.

According to the shaft for a golf club and the golf club provided with the shaft for a golf club manufactured by the present invention, the deflection of the head in the downward direction near the impact point is reduced, and the force is concentrated in the hitting direction, thereby increasing the head speed.

Drawings

Fig. 1 is a configuration diagram of a golf club 1 according to an embodiment.

Fig. 2 is a schematic view showing a mandrel for manufacturing a shaft for a golf club according to an embodiment and a state after respective prepreg sheets wound around the mandrel are spread.

Fig. 3 is a schematic view showing a wound state of prepreg sheets forming the shaft 10 in one embodiment.

Fig. 4 is a schematic view showing a wound state of prepreg sheets forming the shaft 10 in one embodiment.

Fig. 5 is a schematic view showing a wound state of prepreg sheets forming the shaft 10 in one embodiment.

Fig. 6 is a schematic view showing a wound state of prepreg sheets forming the shaft 10 in one embodiment.

Fig. 7 is a schematic view showing a wound state of prepreg sheets forming the shaft 10 in one embodiment.

Fig. 8 is a schematic view showing a wound state of prepreg sheets forming the shaft 10 in one embodiment.

Description of the symbols

1-a golf club; 10-a shaft for golf club; 20-a golf club head; 21-layer 1; 22-prepreg sheet; 23-layer 2; 24-prepreg sheets; 25-layer 3; 26-axial prepreg sheet (first axial prepreg sheet); 27-layer 4; 28-axial prepreg sheet (second axial prepreg sheet); 29-layer 5; 30-axial prepreg sheet (third axial prepreg sheet); 31-inner reinforcing layer; 32-prepreg sheets; 33-outer reinforcing layer; 35-a handle.

Detailed Description

Various embodiments of the present invention will be described below with reference to the accompanying drawings. In the drawings, the same reference numerals are given to the common components.

Fig. 1 is a schematic diagram showing a configuration of a golf club 1 including a golf club shaft (hereinafter, referred to simply as "shaft") 10 according to an embodiment of the present invention. As shown in the figure, the golf club 1 includes: a golf club grip 35 formed of natural rubber, synthetic rubber, or the like; a shaft 10 coupled to the golf club grip 35 and formed in a tubular shape by fiber-reinforced resin; and a golf club head 20 coupled to the shaft 10 through a hosel HZ. Here, the central axis of the shaft 10 is set as the axis X.

Although the golf club head 20 is shown as a wood-type example, a golf club head of a iron-type is also included, and is not limited to a specific form. The golf club head 20 (hereinafter, referred to as the head 20) is made of a metal material such as stainless steel, titanium, or a titanium alloy.

Next, referring to fig. 2, a basic method of forming the shaft 10 according to the present invention by winding and laminating the

prepreg sheets

22, 24, 26, 28, 30, 32, 34 around the mandrel 40 will be briefly described.

The outer periphery between the tip end 40a and the tip end 40b of the mandrel 40 is formed as a tapered surface having a slope of about 1000 to 8, for example, with respect to the central axis C. In manufacturing the shaft 10, a prepreg sheet 32 as an inner reinforcing layer 31 is wound around the tip end 40a of the mandrel 40, and the fiber direction of the reinforcing fibers is the axial direction of the mandrel 40 (the direction substantially along the axial direction of the shaft 10).

Next, the cross prepreg sheet 22 inclined at ± 45 degrees with respect to the axial direction of the mandrel 40 is wound to form the 1 st layer 21 of the shaft 10. The prepreg 22 of the 1 st layer 21 has a portion (hereinafter referred to as an overlap amount) 52 (described in detail later) where the

end portions

22a and 22b are close to each other and overlap each other.

Next, a prepreg sheet 24 having a fiber direction of reinforcing fibers in a direction inclined at 90 degrees with respect to the axial direction of the mandrel 40 is wound to form the layer 2 23 of the shaft 10. The prepreg 24 as the 2 nd layer 23 is formed with an overlapping amount 54 (not shown) by which the

end portions

24a, 24b are brought close to each other and overlapped. The overlapping amount 52 (not shown) of the 1 st layer 21 and the overlapping amount 54 (not shown) of the 2 nd layer 23 may be wound so that the overlapping amounts 52, 54 are arranged at positions shifted from each other with respect to the center axis C of the shaft 10. In addition, the same overlapping amount and gap may not be formed in the relative positions of the overlapping amount and the gap. The prepreg 24 may be simultaneously wound after being laminated to the prepreg 22 or the prepreg 26 described later.

Next, an axial prepreg 26 (first axial prepreg) is wound around the entire axial length of the mandrel 40 to form the 3 rd layer 25 of the shaft 10, the axial prepreg 26 having a fiber direction of the reinforcing fibers along the axial direction. At this point, the winding is performed with the end 26a of the axial prepreg 26 aligned with the mark (not shown) of the mandrel 40. The prepreg 26 in the axial direction as the 3 rd layer 25 is formed with an overlap amount 56 (see fig. 3) in which the

end portions

26a and 26b are close to each other and overlap each other. That is, the

end portions

26a, 26b of the axial prepreg 26 are in a state of being close to each other.

Next, the 4 th layer 27 of the shaft 10 is formed by winding an axial prepreg sheet 28 (second axial prepreg sheet) over the entire axial length of the mandrel 40, the axial prepreg sheet 28 having a fiber direction of the reinforcing fibers along the axial direction. At this point, the winding is performed with the end 28a of the axial prepreg sheet 28 aligned with the mark (not shown) of the mandrel 40. The prepreg 28 in the axial direction as the 4 th layer 27 is formed with an overlap 58 (see fig. 3) in which the

end portions

28a and 28b are close to each other and overlap each other. That is, the

end portions

28a, 28b of the axial prepreg sheet 28 are in a state of being close to each other.

Next, an axial prepreg 30 (third axial prepreg) having a fiber direction of reinforcing fibers along the axial direction is wound around the entire axial length of the mandrel 40 to form the 5 th layer 29 of the shaft 10. At this point, the winding is performed with the end 30a of the axial prepreg 30 aligned with the mark 46 of the mandrel 40. The prepreg 30 in the axial direction as the 5 th layer 29 is formed with an overlap amount 60 (see fig. 3) in which the

end portions

30a and 30b are close to each other and overlap each other. That is, the

end portions

30a and 30b of the axial prepreg 30 are in a state of being close to each other.

The widths x (described in detail later) of the overlapping amounts 56, 58, and 60 of the 3 rd, 4 th, and 5 th layers 25, 27, and 29 formed of the axial prepreg sheets may be respectively 0mm (uniform) or a width of 0 to 3mm inclusive. For example, the width of the overlapping amounts 56, 58, 60 may be in the range of 1 to 3mm or in the range of 2 to 3mm, but is not limited thereto. The widths of the overlapping amounts 56, 58, and 60 may be different depending on the position of the mandrel 40 in the axial direction.

In addition, one of the widths x of the overlapping amounts 58 of the outer 4 th layer 27 is smaller than the overlapping amount 56 of the inner 3 rd layer 25, and one of the widths x of the overlapping amounts 60 of the outer 5 th layer 29 is smaller than the overlapping amount 58 of the inner 4 th layer 27, that is, the widths x of the overlapping amounts 56, 58, 60 may be gradually decreased or increased from the inner layer toward the outer layer.

Finally, the prepreg sheet 34 as the outer reinforcing layer 33 is wound around the tip end 40a of the mandrel 40 so that the fiber direction of the reinforcing fibers is along the axial direction of the mandrel 40. At this time, the cross section of the shaft 10 is in a state shown in fig. 3 described later (illustration of the mandrel 40 is omitted).

Thereafter, similarly to the usual shaft forming, the 5 th layer 29 is fastened with a tape from the outside, thereafter the layers are heat-cured, the mandrel 40 and the tape are removed, and finally, finishing by surface grinding or the like is performed to complete the shaft 10.

The structure of the golf club shaft 10 molded by the above-described manufacturing method will be described with reference to fig. 3 to 8. The steps, gaps, and the like in the appearance of the shaft 10 shown in fig. 3 to 8 are formed along the outer diameter of the mandrel 40 due to the pressure during firing, the flow of the sheet, and the like, and the gaps are also filled. That is, the final outer shape of the shaft 10 is not a shape schematically shown in fig. 3 to 8, but an inner circumference and an outer circumference are smoothly formed so that the cross section becomes a circular ring shape due to the flow of the band, the sheet, and the like.

Fig. 3 to 8 each show a cross section perpendicular to the longitudinal direction of the golf club shaft 10. In each drawing, the position opposite to the position of the downward direction of the head is set as a reference position (0 degrees), and the 1-cycle is divided into 8 parts, and the positions are indicated by 45 degrees, 90 degrees, 135 degrees, 180 degrees (the position of the downward direction of the head), 225 degrees, 270 degrees (the position of the hitting direction), 315 degrees, and 360 degrees (the reference position: 0 degrees), respectively.

For convenience of explanation, fig. 3 to 8 only show the 3 rd, 4 th and 5 th layers of prepreg sheets in the axial direction parallel to the axial direction of the shaft among the prepreg sheets shown in fig. 2. The angular positions are not mathematically strict, but may be substantially the same angular positions.

As described above, the shaft 10 for a golf club is a hollow shaft 10 formed by winding and laminating prepreg sheets in which a synthetic resin is impregnated into reinforcing fibers around a mandrel 40 and performing heat treatment, and includes at least 3 axial prepreg sheets (26, 28, 30) in which the reinforcing fibers are aligned along the axial direction over the entire axial length of the shaft 10, and the axial prepreg sheets are configured such that the winding start position and the winding end position thereof are aligned or partially overlapped in the circumferential direction of the shaft 10 and are located at a position greater than 90 degrees and less than 270 degrees in the circumferential direction from the reference position of the shaft 10, or at a position less than 90 degrees or greater than 270 degrees in the circumferential direction.

According to the golf club shaft 10 of the present invention, the head speed can be increased by reducing downward deflection of the head near the impact point and concentrating the force in the hitting direction.

The axial prepreg sheets (26, 28, 30) of the shaft 10 for a golf club according to one embodiment of the present invention are configured to be aligned or overlapped in the circumferential direction of the shaft 10 between 0mm and 3mm, but are preferably configured to be overlapped between 1mm and 3 mm.

(first embodiment)

Fig. 3 shows the configuration of the golf club shaft 10 according to the first embodiment of the present invention, and the winding start position and the winding end position (the overlap amounts 56, 58, and 60) of the 3 pieces of

axial prepreg sheets

26, 28, and 30 are configured to be 135 degrees, 180 degrees, and 225 degrees from the reference position. Here, each angular position is not necessarily a mathematically strict numerical value, and may be approximately 135 degrees, approximately 180 degrees, or approximately 225 degrees, and more specifically, a range including the angle of about ± 15 degrees (the same applies hereinafter).

In fig. 3, the winding start position and the winding end position (the overlapping amounts 56, 58, and 60) of the 3 pieces of

axial prepreg sheets

26, 28, and 30 are set at 225 degrees, 135 degrees, and 180 degrees from the reference position, respectively, and winding is performed in this order. The overlap (56, 58, 60) was 1 mm.

When 6 subjects measured the difference in head speed between the golf club provided with the shaft according to the first example and the golf club provided with the conventional shaft, it was found that one of the golf clubs provided with the shaft according to the first example could increase the Head Speed (HS). The head is made by using a head attachable to and detachable from a shaft, and elements other than the shaft are omitted as much as possible. Further, as the shaft, the shaft hardness in the hitting direction was selected while being controlled to ± 1 cpm. In addition, a ballistic meter (the same applies hereinafter) was used for measuring the head speed. Specifically, the Head Speed (HS) of 6 subjects who swung at a golf club with a conventional shaft averaged about 39.33m/s, while the head speed averaged about 39.85m/s and increased by 0.52m/s as a result of swinging the golf club with the shaft 10 according to the first example of the present invention. Therefore, it is understood that the golf club including the shaft 10 for a golf club according to the first embodiment of the present invention shown in fig. 3 has an average increase in head speed of 1.3% as compared with the golf club including the conventional shaft. This is considered to be due to the fact that, with the golf club shaft 10 according to the first embodiment of the present invention, the downward deflection of the head near the impact point can be reduced, and the energy in the hitting direction shown in fig. 3 can be more reliably concentrated.

In addition to the above tests, additional tests were performed on 11 subjects. The test results will be described below. As comparative example 1, a shaft in which the respective positions of the winding start position and the winding end position are shifted by 90 degrees in the backswing (back) direction and the striking direction in the form shown in fig. 3 was used. Table 1 shows the results of 11 subjects with respect to the head speed of the golf club using the shaft of comparative example 1 and the head speed of the golf club provided with the shaft 10 according to the first example of the present invention shown in fig. 3. The unit of the head speed is m/s (the same applies hereinafter).

TABLE 1

From the above test results, it is understood that the head speeds of all the subjects were improved in the first example of the present invention with respect to comparative example 1, and the average of them was increased by 1.3% from 40.40m/s to 40.92 m/s.

As described above, according to the golf club shaft 10 of the first embodiment of the present invention, the deflection of the head in the downward direction near the impact point is reduced, and the force is concentrated in the hitting direction, thereby increasing the head speed.

(second embodiment)

Fig. 4 shows a configuration of a golf club shaft 10 according to a second embodiment of the present invention, in which the winding start position and the winding end position (overlap amounts 56, 58, and 60) of 3 pieces of

axial prepreg sheets

26, 28, and 30 are both configured to be 180 degrees. The overlap (56, 58, 60) was 1 mm.

When 6 subjects measured the difference in head speed between the golf club provided with the shaft according to the second example and the golf club provided with the conventional shaft, it was found that the head speed of one of the golf clubs provided with the shaft according to the second example was improved by about 2% on average. This is considered to be due to the fact that, with the golf club shaft 10 according to the second embodiment of the present invention, downward deflection of the head near the impact point can be reduced, and energy in the hitting direction shown in fig. 4 can be more reliably concentrated.

In addition to the above test, another additional test was performed by 12 subjects. The test results will be described below. As comparative example 2, a shaft was used in which the respective positions of the winding start position and the winding end position were shifted by 90 degrees in the backswing direction and the hitting direction in the form shown in fig. 4. Table 2 shows the results of 12 subjects regarding the head speed of the golf club using the shaft of comparative example 2 and the head speed of the golf club provided with the shaft 10 according to the second example.

TABLE 2

From the above test results, it is understood that the head speeds of all the subjects were improved in the second example compared to comparative example 2, and the head speeds were increased by 1.8% from 40.07m/s to 40.78m/s on average.

According to the golf club shaft 10 of the second embodiment of the present invention, the head speed can be increased by reducing the downward deflection of the head near the impact point and concentrating the force more in the hitting direction.

(third embodiment)

Fig. 5 shows that the shaft 10 for a golf club according to the third embodiment of the present invention is configured such that the winding start position and the winding end position (overlapping amounts 56, 58, and 60) of 3 pieces of

axial prepreg sheets

26, 28, and 30 are wound in this order at the positions of 225 degrees, 135 degrees, and 180 degrees, respectively. The overlap (56, 58, 60) was 3 mm.

When 6 subjects measured the difference in head speed between the golf club having the shaft according to the third example and the golf club having the conventional shaft, it was found that the head speed of one of the golf clubs having the shaft according to the third example was improved by about 2% on average. This is considered to be due to the fact that, with the golf club shaft 10 according to the third embodiment of the present invention, downward deflection of the head near the impact point can be reduced, and energy in the hitting direction shown in fig. 5 can be more reliably concentrated.

In addition to the above tests, additional tests were performed on 10 subjects. The test results will be described below. As comparative example 3, a shaft was used in which the respective positions of the winding start position and the winding end position were shifted by 90 degrees in the backswing direction and the hitting direction in the form shown in fig. 5. Table 3 shows the results of 10 subjects with respect to the head speed of the golf club using the shaft of comparative example 3 and the head speed of the golf club provided with the shaft 10 according to the third example.

TABLE 3

From the above test results, it is understood that the head speeds of all the subjects in the third example are improved relative to comparative example 3, and are increased by 1.2% from 39.73m/s to 40.19m/s on average.

According to the golf club shaft 10 of the third embodiment of the present invention, the head speed can be increased by reducing the downward deflection of the head near the impact point and concentrating the force more in the hitting direction.

(fourth embodiment)

Fig. 6 shows a golf club shaft 10 according to a fourth embodiment of the present invention, in which the winding start position and the winding end position (overlap amounts 56, 58, and 60) of 3 pieces of

axial prepreg sheets

26, 28, and 30 are configured to be wound in this order at positions of 45 degrees, 315 degrees, and 0 degree (360 degrees), respectively. The overlap (56, 58, 60) was 1 mm.

When 6 subjects measured the difference in head speed between the golf club having the shaft according to the fourth example and the golf club having the conventional shaft, it was found that the head speed of one of the golf clubs having the shaft according to the fourth example was improved by about 2% on average. This is considered to be due to the fact that, with the golf club shaft 10 according to the fourth embodiment of the present invention, the downward deflection of the head in the vicinity of the impact point can be reduced, and the energy in the hitting direction shown in fig. 6 can be more reliably concentrated.

In addition to the above tests, additional tests were performed by 6 subjects. The test results are described below. As comparative example 4, a shaft was used in which the respective positions of the winding start position and the winding end position were shifted by 90 degrees in the backswing direction and the hitting direction in the form shown in fig. 6. Table 4 shows the results of 6 subjects regarding the head speed of the golf club using the shaft of comparative example 4 and the head speed of the golf club provided with the shaft 10 according to the fourth example.

TABLE 4

From the above test results, it is understood that the fourth example is improved in the head speed of all the subjects relative to comparative example 4, and it is increased by 1.8% from 40.56m/s to 41.28m/s on average.

According to the golf club shaft 10 of the fourth embodiment of the present invention, the head speed can be increased by reducing the downward deflection of the head near the impact point and concentrating the force more in the hitting direction.

(fifth embodiment)

Fig. 7 shows that the winding start position and the winding end position (overlap amounts 56, 58, and 60) of 3 pieces of

axial prepreg sheets

26, 28, and 30 in the shaft 10 for a golf club according to the fifth embodiment of the present invention are both configured to be 0 degree (360 degrees). The overlap (56, 58, 60) was 1 mm.

When 6 subjects measured the difference in head speed between the golf club provided with the shaft according to the fifth example and the golf club provided with the conventional shaft, it was found that the head speed of one of the golf clubs provided with the shaft according to the fifth example was improved by about 2% on average. This is considered to be due to the fact that, with the golf club shaft 10 according to the fifth embodiment of the present invention, downward deflection of the head near the impact point can be reduced, and energy in the hitting direction shown in fig. 7 can be more reliably concentrated.

In addition to the above tests, additional tests were performed by 7 subjects. The test results will be described below. As comparative example 5, a shaft was used in which the respective positions of the winding start position and the winding end position were shifted by 90 degrees in the backswing direction and the hitting direction in the form shown in fig. 7. Table 5 shows the results of 7 subjects regarding the head speed of the golf club using the shaft of comparative example 5 and the head speed of the golf club provided with the shaft 10 according to the fifth example.

TABLE 5

From the above test results, it is understood that the head speeds of all the subjects in the fifth example are improved relative to comparative example 5, and the average increase from 40.51m/s to 41.32m/s is 2.0%.

According to the golf club shaft 10 of the fifth embodiment of the present invention, the head speed can be increased by reducing the downward deflection of the head near the impact point and concentrating the force more in the hitting direction.

(sixth embodiment)

Fig. 8 shows that the shaft 10 for a golf club according to the sixth embodiment of the present invention is configured such that the winding start position and the winding end position (the overlapping amounts 56, 58, and 60) of 3 pieces of

axial prepreg sheets

26, 28, and 30 are wound in this order at positions of 45 degrees, 315 degrees, and 0 degree (360 degrees), respectively. The overlap (56, 58, 60) was 3 mm.

When 6 subjects measured the difference in head speed between the golf club having the shaft according to the sixth example and the golf club having the conventional shaft, it was found that the head speed of one of the golf clubs having the shaft according to the sixth example was improved by about 2% on average. This is considered to be due to the fact that, with the golf club shaft 10 according to the sixth embodiment of the present invention, downward deflection of the head near the impact point can be reduced, and energy in the hitting direction shown in fig. 8 can be more reliably concentrated.

In addition to the above tests, additional tests were performed by 6 subjects. The test results will be described below. As comparative example 6, a shaft was used in which the respective positions of the winding start position and the winding end position were shifted by 90 degrees in the backswing direction and the hitting direction in the form shown in fig. 8. Table 6 shows the results of 6 subjects regarding the head speed of the golf club using the shaft of comparative example 6 and the head speed of the golf club provided with the shaft 10 according to the sixth example.

TABLE 6

From the above test results, it is understood that the head speeds of all the subjects were improved in the fifth example, compared to comparative example 5, and the average of the head speeds was increased by 1.5% from 39.82m/s to 40.42 m/s.

According to the golf club shaft 10 of the sixth embodiment of the present invention, the head speed can be increased by reducing the downward deflection of the head near the impact point and concentrating the force more in the hitting direction.

Although the first to sixth embodiments of the present invention have been described above, in the present invention, the axial prepreg sheets that form the shaft 10 for a golf club and are parallel to the axial direction of the shaft are not limited to 3 sheets shown in fig. 2, and may be 4 or more sheets, as long as at least 3 sheets are provided.

According to the golf club 1 including the golf club shaft 10 according to the present invention, the head speed can be increased by reducing the downward deflection of the head near the impact point and concentrating the force in the hitting direction.

The dimensions, materials, and arrangements of the respective components described in the present specification are not limited to those explicitly described in the embodiments, and the respective components may be modified so as to have any dimensions, materials, and arrangements within the scope of the present invention. In the embodiments described above, components not explicitly described in the present specification may be added, and some of the components described in the embodiments may be omitted.

Claims

1. A method of manufacturing a shaft for a golf club, comprising winding and laminating a plurality of prepreg sheets in which a synthetic resin is impregnated into reinforcing fibers around a mandrel, and then performing a heat treatment,

each of the winding start position and the winding end position of at least 3 pieces of the axial prepreg sheets is any one of a position greater than 90 degrees and less than 270 degrees in the circumferential direction from a reference position of the shaft, a position less than 90 degrees in the circumferential direction from the reference position of the shaft, and a position greater than 270 degrees.

2. The method of manufacturing the shaft for a golf club according to claim 1, wherein a winding start position and a winding end position of at least 3 pieces of the axial prepreg sheets overlap each other by 0 to 3 mm.

3. The method of manufacturing the shaft for a golf club according to claim 1 or 2, wherein the winding start position and the winding end position of at least 3 pieces of the axial prepreg sheets are positions of 135 degrees, 180 degrees, and 225 degrees from the reference position, respectively.

4. The method of manufacturing the shaft for a golf club according to claim 1 or 2, wherein the winding start position and the winding end position of at least 3 pieces of the axial prepreg sheets are 225 degrees, 135 degrees, and 180 degrees from the reference position, respectively, and the winding is performed in this order.

5. The method of manufacturing the shaft for a golf club according to claim 1 or 2, wherein the winding start position and the winding end position of at least 3 pieces of the axial prepreg sheets are positions of 315 degrees, 0 degrees, and 45 degrees from the reference position, respectively.

6. The method of manufacturing the shaft for a golf club according to claim 1 or 2, wherein the winding start position and the winding end position of at least 3 pieces of the axial prepreg sheets are positions at 45 degrees, 315 degrees and 0 degrees from the reference position, respectively, and the winding is performed in this order.

7. The method of manufacturing the shaft for a golf club according to claim 1 or 2, wherein the winding start position and the winding end position of at least 3 pieces of the axial prepreg sheets are both positions 180 degrees from the reference position.

8. The method of manufacturing the shaft for a golf club according to claim 1 or 2, wherein the winding start position and the winding end position of at least 3 pieces of the axial prepreg sheets are both positions of 0 degree from the reference position.

9. The method of manufacturing a shaft for a golf club according to claim 1 or 2, wherein the reference position is a position opposite to a position in a downward direction of a head on a cross section of the shaft perpendicular to a longitudinal direction.

10. The method of manufacturing the shaft for a golf club according to claim 1 or 2, further comprising a prepreg sheet in which the reinforcing fibers are aligned in an oblique direction or a perpendicular direction with respect to an axial direction of the shaft, in at least 3 layers inside the unidirectional prepreg sheet.

11. The method of manufacturing the shaft for a golf club according to claim 1 or 2, further comprising a prepreg sheet as an inner reinforcing layer and/or an outer reinforcing layer in an innermost layer and/or an outermost layer of the tip end portion of the shaft.

12. A shaft for a golf club manufactured by the method of any 1 of claims 1 to 11, having at least 3 reinforcing fiber layers aligning a fiber direction in an axial direction over an entire axial length of the shaft.

13. A golf club comprising the shaft for a golf club according to claim 12 and a golf club head attached to a tip end of the shaft for a golf club.