Patent Application
20240359070
The present invention relates to a golf shaft realizing a low trajectory and low spin and a manufacturing method for the same.
In a golf club, it is known that carry of a ball is improved by a higher trajectory and lower spin. Such a ball with a high trajectory and low spin is realized by adjustment of rigidity distribution of a shaft (golf shaft) for a golf club like, for example, Patent document 1.
The ball with the high trajectory and the low spin is affected by wind and may not be improved in carry. In this case, it is advantageous to lower a trajectory to make a ball be a low trajectory and low spin.
Although the ball with the low trajectory and the low spin is supposedly realized by improving rigidity of a tip end of a golf shaft in general, it is insufficient to simply improve the rigidity of the tip end.
A problem to be solved is that a sufficient low trajectory and sufficient low spin are not realized.
The present invention provides a golf shaft, having a rigidity distribution in which rigidity gradually increases from a tip end section to a butt end section, wherein the rigidity distribution has an intermediate point at which inclination is changed in an intermediate section between the tip end section and the butt end section, a difference in rigidity between the tip end section and the intermediate point is 3.00 kgf·m2-5.00 kgf. m2, and a difference in rigidity between the intermediate point and the butt end section is 2.00 kgf·m2or less.
Further, the present invention provides a manufacturing method of a golf shaft having a rigidity distribution in which rigidity gradually increases from a tip end section to a butt end section, comprising extending a length of the butt end section in an axial direction by one or more adjustment steps with respect to a basic shape, and eliminating the adjustment steps corresponding to an amount of the extending of the length of the butt end section with respect to the basic shape, the basic shape in which an intermediate section between the tip end section and the butt end section has a main body, a plurality of adjustment steps having different outer diameters located on a tip end side relative to the main body, and a straight portion having a constant outer diameter located on the tip end side relative to the adjustment steps.
According to the golf shaft of the present invention, the rigidity at the tip end section and the butt end section are set appropriately in relation to the intermediate point to realize a sufficient low trajectory and sufficient low spin.
According to the manufacturing method for a golf shaft, a plurality of flexes are easily developed in golf shafts in which rigidity gradually increases from a tip end section to a butt end section including a golf shaft realizing a sufficient low trajectory and sufficient low spin.
The object of realizing a sufficient low trajectory and sufficient low spin is accomplished by a rigidity distribution of a golf shaft.
Namely, a golf shaft (1) has a rigidity distribution in which rigidity gradually increases from a tip end section (5) to a butt end section (7). The rigidity distribution has an intermediate point (P) at which inclination is changed in an intermediate section (9) between the tip end section (5) and the butt end section (7), a difference in rigidity between the tip end section (5) and the intermediate point (P) is 3.00 kgf·m2-5.00 kgf·m2, and a difference in rigidity between the intermediate point (P) and the butt end section (7) is 2.00 kgf·m2or less.
The intermediate point (P) may be located in a range having a distance from a tip end of the golf shaft (1) being 40%-60% of an entire length.
The golf shaft (1) is formed into a stepped shape exhibited between the tip end section (5) and the butt end section (7) so that an outer diameter is gradually increased, and the stepped shape has a difference in outer diameter between adjacent steps (13) from the intermediate point (P) to the butt end section (7) being smaller than a difference in outer diameter between adjacent steps (13) from the tip end section (5) to the intermediate point (P).
A manufacturing method for a golf shaft is a method of manufacturing the golf shaft (1) having a rigidity distribution in which rigidity gradually increases from a tip end section (5) to a butt end section (7). The manufacturing method extends a length of the butt end section (7) in an axial direction by one or more adjustment steps (13) with respect to a basic shape, and eliminates the adjustment steps (13) corresponding to an amount of the extending of the length of the butt end section (7) with respect to the basic shape, the basic shape in which an intermediate section (9) between the tip end section (5) and the butt end section (7) has a main body (11), a plurality of adjustment steps (13) having different outer diameters located on a tip end side relative to the main body (11), and a straight portion (15) having a constant outer diameter and located on the tip end side relative to the adjustment steps (13).
In the manufacturing method, an outer diameter of the straight portion (15) may be made equivalent to a largest outer diameter in the eliminated adjustment steps (13).
A golf shaft 1 of the present embodiment is a metal shaft and is made of a metal hollow tube. The golf shaft 1 has an outer diameter being a stepped shape as a whole and being gradually increased. A sectional shape of the golf shaft 1 in a traverse section is a circular shape. It should be noted that the outer diameter of the golf shaft 1 may not be a stepped shape and may be other shapes of which part or a whole is a tapered shape or the like. In addition, the traverse sectional shape of the golf shaft 1 may be another shape such as oval.
A length of the golf shaft 1 is 37-41 inches (about 93.98-104.14 cm). The golf shaft 1 may be, however, set shorter than 37 inches or longer than 41 inches. Further, although material of the golf shaft 1 is steel, it may be other material. The other material is other metal such as aluminum, titanium, or alloy thereof, non-metal such as CFRP, composite material that is a combination of metal and non-metal, or the like.
The golf shaft 1 is composed of a tip end section 5, a butt end section 7, and an intermediate section 9.
The tip end section 5 is a tip end portion in an axial direction and is a region having a given range from a tip end of the golf shaft 1 in the axial direction. The tip end section 5 of the present embodiment is a portion to which a head of a golf club is attached. The tip end section 5 is formed into a tapered shape having an outer diameter slightly gradually increases toward a butt end of the golf shaft 1. The tip end section 5 may be, however, formed into a straight shape having a constant outer diameter.
The butt end section 7 is a butt end portion of the golf shaft 1 in the axial direction and is a region having a given range from the butt end of the golf shaft 1 in the axial direction. The butt end section 7 of the present embodiment is a portion to which a grip of the golf club is attached. Although the butt end section 7 is formed into a straight shape having a constant outer diameter, it may be a tapered shape having an outer diameter is slightly gradually varied toward the butt end.
The intermediate section 9 is a portion located between the tip end section 5 and the butt end section 7, and is composed of a main body 11, a plurality of adjustment steps 13, a straight portion 15, and a tapered portion 16.
The main body 11 is a portion entirely formed into the stepped shape and is composed of a plurality of steps 17. The plurality of the steps 17 are gradually increased in outer diameter toward the butt end. In each step 17, the outer diameter is constant and the outer diameter may be gradually increased toward the butt end.
In the stepped shape of the main body 11, a difference in outer diameter between adjacent steps 13 from the intermediate point P to the butt end section 7 is smaller than a difference in outer diameter between adjacent steps 13 from the tip end section 5 to the intermediate point P (see
The main body 11 is a portion that is not changed in shape regardless of variations of the golf shaft 1 in flex. The flex of the golf shaft 1 is rigidity of the golf shaft 1 and a plurality of flexes are developed even in the same golf shaft 1 in general.
The plurality of the adjustment steps 13 are steps to adjust the golf shaft 1 in flex. The number of the adjustment steps 13 is reduced as the flex becomes harder as explained later. The golf shaft 1 may, therefore, have no adjustment steps 13 according to the flex. In addition, the adjustment steps 13 may not be provided regardless of the flex.
The plurality of the adjustment steps 13 are located on the tip end side relative to the main body 11 and have different outer diameters. According to the present embodiment, the adjustment steps 13 entirely exhibit a stepped shape adjoining to the main body 11 and is continuous to the stepped shape of the main body 11. These adjustment steps 13 are gradually increased in outer diameter toward the butt end similarly to the steps 17 of the main body 11.
It should be noted that the adjustment steps 13 are not necessarily adjoining to the main body 11 and tapered portions, steps or the like may be interposed between the adjustment steps 13 and the main body 11.
An outer diameter of each adjustment step 13 is constant. The outer diameter of the adjustment step 13 may be, however, gradually increased toward the butt end. The plurality of the adjustment steps 13 have the same axial length. The axial lengths of the plurality of the adjustment steps 13 may be, however, different from each other according to flex development.
The straight portion 15 is a portion located on the tip end side relative to the adjustment steps 13 and having a constant outer diameter. In addition, the straight portion 15 may be interposed between the tip end section 5 and the main body 9 of the intermediate section 9 if the adjustment steps 13 are omitted.
The straight portion 15 of the present embodiment is interposed between the tip end section 5 and the adjustment steps 13, an outer diameter of which is smaller than the smallest one of the adjustment steps 13 and larger than of the tip end section 5. The outer diameter of the straight portion 15 is set larger as the flex becomes harder as explained later. In addition, although the straight portion 15 is adjoining to the adjustment step 13, tapered portions, steps or the like may be interposed between the adjustment step 13 and the straight portion 15.
The tapered portion 16 is a portion having a tapered shape arranged between the straight portion 15 and the tip end section 5, to absorb a difference in diameter between the straight portion 15 and the tip end section 5.
The golf shaft 1 with the above structure has a rigidity distribution in which rigidity gradually increases from the tip end section 5 to the butt end section 7. It should be noted that the gradually increasing of the rigidity means that, in the rigidity distribution, inclination of approximation straight line of a segment from the tip end section 5 to the butt end section 7, inclination of a segment connecting the tip end section 5 and the butt end section 7, an average of inclinations of a segment from the tip end section 5 to the butt end section 7 or the like is positive. In that sense, the gradually increasing of the rigidity includes a case in which the rigidity is barely reduced between the tip end section 5 and the butt end section 7.
In the case that the rigidity is reduced, a permissible reduction amount of the rigidity is 10% or less of a difference in rigidity between the tip end section 5 and the butt end section 7 in order to realize a sufficient low trajectory and sufficient low spin. The reduction amount is a difference in rigidity between a peak on the tip end side and a valley on the butt end side that are adjacent to each other in the rigidity distribution.
As the rigidity distribution of
In the rigidity distribution, the intermediate section 9 has the intermediate point P at which inclination is changed. This inclination means inclination on the tip end side and inclination on the butt end side relative to the intermediate point P as a center. In addition, the intermediate point P means not only a point at which the inclination is changed on the rigidity distribution but also an axial part of the golf shaft 1 corresponding to the point in the present specification.
The inclination on the tip end side is inclination of approximation straight line of a segment from the tip end section 5 to the intermediate point P, inclination of a segment connecting the tip end section 5 and the intermediate point P, an average of inclinations of the segment from the tip end section 5 to the intermediate section 9 or the like. The inclination on the butt end side is inclination of approximation straight line of a segment from the intermediate point P to the butt end section 7, inclination of a segment connecting the intermediate point P and the butt end section 7, an average of inclinations of the segment from the intermediate section 9 to the butt end section 7 or the like.
The inclination on the tip end side is larger than the inclination on the butt end side. This is adjustable according to the difference in outer diameter and axial dimension between the adjacent steps 17 of the stepped shape.
In the rigidity distribution, a difference in rigidity between the tip end section 5 and the intermediate point P is 3.00 kgf·m2-5.00 kgf·m2 and the difference in rigidity between the intermediate point P and the butt end section 7 is 2.00 kgf·m2or less. Although the rigidity at the tip end section 5 is rigidity at a position of 50 mm from the tip end in this embodiment, it may be an average value, a maximum value, a minimum value or the like in the tip end section 5 if the rigidity of the tip end section 5 is varied. The rigidity of the butt end section 7 is rigidity at any position of the butt end section 7. If the rigidity of the butt end section 7 is varied in the axial direction, it may be, however, an average value, a maximum value, a minimum value or the like.
The intermediate point P is preferably located in a range having a distance from the tip end of the golf shaft 1 being 40%-60% of the entire length of the golf shaft 1. The rigidity of the intermediate point P is preferably 5.40 kgf·m2-8.00 kgf·m2. More preferably, the rigidity of the tip end section 5 is 2.20 kgf·m2or more and the rigidity of the butt end section 7 is 9.00 kgf·m2or less. According to the present embodiment, the position of the intermediate point P is a position at 50% of the entire length and the rigidity of the intermediate point P is 6.06 kgf·m2. The rigidity of the tip end section 5 is 2.30 kgf·m2 and the rigidity of the butt end section 7.39 kgf·m2. In addition, the position and the rigidity of the intermediate point P, the rigidity of the tip end section 5 and the butt end section 7 may employ values other than the above.
Further, in the present embodiment, the rigidity is set so as not to exceed 4.00 kgf·m2 from the tip end to a position at 20% of the entire length.
With this rigidity distribution, the golf shaft 1 of the present embodiment has the rigidity of the tip end section 5 set higher and the rigidity of the butt end section 7 set lower in relation to the intermediate point P, thereby delaying in bending and reducing a hitting angle. Further, the rigidity of the intermediate point P is high to reduce a spin amount. As this result, the golf shaft 1 of the present embodiment realizes the sufficient low trajectory and the sufficient low spin.
The comparative example 1 is for a low trajectory and non-low spin, the comparative example 2 is for a high trajectory and low spin, the comparative example 3 is for a general trajectory and general spin.
The comparative example 1 is set higher in rigidity on the tip end section side and lower in rigidity on the butt end in comparison with the comparative example 3. The comparative example 2 is set higher in rigidity of an entire area spanning from the intermediate section to the butt end section in comparison with the comparative example 3.
In contrast, the present embodiment is set higher in rigidity from the tip end section to the intermediate section and lower in rigidity from the intermediate section to the butt end section in comparison with the comparative example 3. Further, in the present embodiment, the rigidity of the intermediate section 9 is positioned between of the comparative examples 1 and 2.
With the difference, the present embodiment reduces the spin amount while equalizing the hitting angle in comparison with the comparative example 1 in which the rigidity on the tip end section side is simply improved. Further, the spin amount is further reduced relative to the comparative example 2 for the low spin.
The manufacturing method for the golf shaft 1 of the present embodiment, for example, rolls a plate material to form a pipe body, inner and outer diameters of which are constant. To the pipe body, stepping process is performed and the wall thickness is set.
At this time, the present embodiment sets the axial length of the butt end section 7, the number of the adjustment steps 13 and the outer diameter of the straight portion 15, thereby adjusting the flex.
The adjustment of the flex is performed relatively to a basic shape of
In the basic shape, the intermediate section 9 has the main body 11, a plurality of the adjustment steps 13, and the straight portion 15. According to the present embodiment, the basic shape has three adjustment steps 13 and, by that, the butt end section 7 is set shorter than the golf shaft 1 of
The adjustment of the flex is performed by, with respect to the basic shape, extending the length of the butt end section 7 in the axial direction by one or more adjustment steps 13 and eliminating the adjustment steps 13 corresponding to an amount of the extending of the length of the butt end section 7. With this, the flex is adjusted without changing the rigidity distribution of the main body 11.
Further, the outer diameter of the straight portion 15 is made equivalent to a largest outer diameter in the eliminated adjustment steps 13. With this, the rigidity on the tip end side is increased to suppress increase of the inclination of the rigidity distribution from the tip end section 5 to the intermediate point P. At this time, the tapered portion 16 is formed to absorb the difference in outer diameter between the tip end section 5 and the straight portion 15.
It should be noted that the adjustment of the flex (manufacturing method) of the present embodiment is applicable to a golf shaft other than the golf shaft 1 for the low trajectory and the low spin. In the other golf shaft, increase of inclination in the rigidity distribution from a tip end section 5 to an intermediate point P may not be suppressed at the time of adjustment of a flex. In this case, an outer diameter of a straight portion 15 is not necessarily changed at the time of the adjustment of the flex and may remain the basic shape.
The golf shaft 1 of
In the golf shafts 1 of
With the settings of the outer diameters, the difference in outer diameter between the tip end section 5 and the straight portion 15 is increased in the golf shafts 1 of
As illustrated in
As mentioned above, the golf shaft 1 of the present embodiment, in the rigidity distribution gradually increasing from the tip end section 5 to the butt end section 7, has the intermediate point P at which the inclination is changed in the intermediate section 9 between the tip end section 5 and the butt end section 7, the difference in rigidity between the tip end section 5 and the intermediate point P of the intermediate section 9 being 3.00 kgf·m2-5.00 kgf·m2and the difference in rigidity between the intermediate point P of the intermediate section 9 and the butt end section 7 being 2.00 kgf·m2or less.
Accordingly, the golf shaft 1 of the present embodiment has the rigidity of the tip end section 5 set higher and the rigidity of the butt end section 7 set lower in relation to the intermediate point P, thereby surely reducing the hitting angle and the spin amount. As this result, the golf shaft 1 of the present embodiment realizes the sufficient low trajectory and the sufficient low spin.
Further, since the intermediate point P is located in the range having the distance from the tip end of the golf shaft 1 being 40%-60% of the entire length of the golf shaft 1, so that the golf shaft 1 more surely realizes the low trajectory and the low spin.
The golf shaft 1 has the stepped shape exhibited between the tip end section 5 and the butt end section 7 so that the outer diameter is gradually increased, and the stepped shape has the difference in outer diameter between the adjacent steps 17 from the intermediate point P to the butt end section 7 being smaller than the difference in outer diameter between the adjacent steps 17 from the tip end section 5 to the intermediate point P.
Accordingly, the golf shaft 1 capable of realizing the low trajectory and the low spin is easily and surely obtained.
The manufacturing method for the golf shaft 1 of the present embodiment extends the length of the butt end section 7 in the axial direction by one or more adjustment steps 13 with respect to the basic shape, and eliminates the adjustment steps corresponding to the amount of the extending of the length of the butt end section 7 with respect to the basic shape, to manufacture the golf shafts 1 with the different flexes. With this, the present embodiment performs the flex development without changing of the rigidity distribution of the main body 11. Further, the present embodiment discriminates the flex according to the number of the adjustment steps 13 of the manufactured golf shaft 1 in appearance. Further, the planed flex development is easily performed according to setting in length and diameter of the adjustment steps 13.
Furthermore, the present embodiment makes the outer diameter of the straight portion 15 equivalent to the largest outer diameter in the eliminated adjustment steps 13. The flex development is, therefore, easily performed in the golf shaft 1 for the low trajectory and the low spin.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2021-115758 | Jul 2021 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2022/008647 | 3/1/2022 | WO |
