US20130324289A1 - Golf club steel shaft - Google Patents
Golf club steel shaft Download PDFInfo
- Publication number
- US20130324289A1 US20130324289A1 US13/905,311 US201313905311A US2013324289A1 US 20130324289 A1 US20130324289 A1 US 20130324289A1 US 201313905311 A US201313905311 A US 201313905311A US 2013324289 A1 US2013324289 A1 US 2013324289A1
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- United States
- Prior art keywords
- shaft
- golf club
- weight
- head
- ball
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- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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- A—HUMAN NECESSITIES
- A63—SPORTS; GAMES; AMUSEMENTS
- A63B—APPARATUS FOR PHYSICAL TRAINING, GYMNASTICS, SWIMMING, CLIMBING, OR FENCING; BALL GAMES; TRAINING EQUIPMENT
- A63B53/00—Golf clubs
- A63B53/12—Metallic shafts
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- A—HUMAN NECESSITIES
- A63—SPORTS; GAMES; AMUSEMENTS
- A63B—APPARATUS FOR PHYSICAL TRAINING, GYMNASTICS, SWIMMING, CLIMBING, OR FENCING; BALL GAMES; TRAINING EQUIPMENT
- A63B60/00—Details or accessories of golf clubs, bats, rackets or the like
-
- A—HUMAN NECESSITIES
- A63—SPORTS; GAMES; AMUSEMENTS
- A63B—APPARATUS FOR PHYSICAL TRAINING, GYMNASTICS, SWIMMING, CLIMBING, OR FENCING; BALL GAMES; TRAINING EQUIPMENT
- A63B60/00—Details or accessories of golf clubs, bats, rackets or the like
- A63B60/42—Devices for measuring, verifying, correcting or customising the inherent characteristics of golf clubs, bats, rackets or the like, e.g. measuring the maximum torque a batting shaft can withstand
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- A—HUMAN NECESSITIES
- A63—SPORTS; GAMES; AMUSEMENTS
- A63B—APPARATUS FOR PHYSICAL TRAINING, GYMNASTICS, SWIMMING, CLIMBING, OR FENCING; BALL GAMES; TRAINING EQUIPMENT
- A63B2225/00—Miscellaneous features of sport apparatus, devices or equipment
- A63B2225/02—Testing, calibrating or measuring of equipment
Definitions
- the present invention relates to a steel shaft.
- flight distance of a ball is one of the important factors when selecting a golf club. Therefore, hitherto, in order to extend the flight distance of the ball, various improvements have been made with regard to shapes and materials of elements forming a golf club.
- the present invention has been made in view of such circumstances, and an objective of the present invention is to provide a golf club steel shaft that makes it possible to extend flight distance of a ball while maintaining feel of hitting a ball and directivity of a hit ball.
- the center-of-gravity rate Y (%), the shaft weight X (g), and the full length of the shaft L S (inch) are each set as values within the above described ranges, it is possible to increase weight of a golf club head with steel iron, and extend flight distance of a ball while maintaining feel of hitting a ball and directivity of a hit ball.
- a thickness of a portion up to 150 mm from a butt end toward a front end side of the shaft is preferably not smaller than 0.30 mm but not larger than 0.40 mm.
- an outer diameter of a portion up to 150 mm from a butt end toward a front end side of the shaft is preferably not smaller than 14.5 mm but not larger than 15.3 mm.
- the number of steps included in a portion up to 400 mm from a butt end toward a front end side of the shaft is preferably not less than 5 but not more than 8.
- FIG. 1 is an illustrative diagram of a golf club including one embodiment of a golf club steel shaft of the present invention.
- FIG. 2 is for describing a method for measuring T-point strength.
- FIG. 1 is an illustrative diagram showing the entirety of a golf club 1 including a steel shaft (hereinafter, may be simply referred to as “shaft”) for a golf club, according to one embodiment of the present invention.
- the golf club 1 includes an iron type golf club head 2 having a predetermined loft angle, a shaft 3 , and a grip 4 .
- the head 2 has a hosel 6 including a shaft hole 5 to which a tip end 3 a on the front end side of the shaft 3 is inserted and fixed.
- a butt end 3 b at the back end side of the shaft 3 is inserted and fixed in a grip hole 7 of the grip 4 .
- the tip end 3 a is positioned inside the head 2
- the butt end 3 b is positioned inside the grip 4 .
- a reference character of “G” indicates the center of gravity (center of gravity point) of the shaft 3 .
- the center of gravity G is located on a shaft axis inside the shaft 3 .
- the weight of the golf club 1 is not particularly limited in the present invention, it is preferably set within a range of not smaller than 360 g. If the weight of the golf club 1 is too small, the strengths of respective elements (parts) forming the golf club 1 become low, and durability of the golf club 1 may deteriorate. Therefore, the weight of the golf club 1 is preferably not smaller than 370 g, and further preferably not smaller than 380 g. On the other hand, if the weight of the golf club 1 is too large, it becomes difficult to perform a swing, and it becomes difficult to increase head speed. Therefore, the weight of the golf club 1 is further preferably not larger than 500 g, and particularly preferably not larger than 490 g.
- the length of the golf club 1 itself is also not particularly limited in the present invention, and is ordinarily from 34.0 to 42.0 inches. If the length of the golf club 1 is too small, although a swing can be performed easily, a turning radius of the swing becomes small, and it becomes difficult to obtain a sufficient head speed. As a result, the ball speed cannot be increased, and the flight distance of the ball cannot be extended. Therefore, the length of the golf club 1 is preferably not smaller than 34.5 inches, and further preferably not smaller than 35.0 inches. On the other hand, if the length of the golf club 1 is too large, the head speed decreases since it becomes difficult to swing the club. Therefore, the ball speed cannot be increased, and the flight distance of the ball cannot be extended. Therefore, the length of the golf club 1 is preferably not larger than 41.5 inches, and further preferably not larger than 41.0 inches.
- club length is a length measured based on the description in “Appendix II—Design of Clubs” “1. Clubs” “1c. Length” in the Rules of Golf determined by R&A (The Royal and Ancient Golf Club of Saint Andrews).
- the head 2 in the present embodiment is a solid iron head and has a large inertia moment. With a club having the head 2 with a large inertia moment, an advantageous effect of improvement in flight distance can be stably obtained.
- the material of the head 2 there is no particular limitation in the material of the head 2 , and, for example, titanium, titanium alloys, stainless steel, maraging steel, soft iron, and the like can be used. Furthermore, instead of manufacturing the head 2 using a single material, the head 2 may be manufactured by combining multiple materials as appropriate.
- the weight of the head 2 itself is not particularly limited, it is preferably within a range from 230 to 310 g. If the head 2 is too light, the kinetic energy of the head 2 cannot be sufficiently provided to the ball, and it becomes difficult to increase the ball speed. Therefore, the weight of the head 2 is further preferably not smaller than 235 g, and particularly preferably not smaller than 240 g. On the other hand, if the weight of the head 2 is too large, the golf club 1 becomes heavy and difficult to swing. Therefore, the weight of the head 2 is further preferably not larger than 305 g, and particularly preferably not larger than 300 g.
- the ratio (head weight/club weight) of the head weight and the club weight is set to be not lower than 0.55 but not higher than 0.70. If this ratio is too small, the kinetic energy of the head 2 becomes small and obtaining a sufficient ball speed becomes difficult. Therefore, the ratio is preferably not lower than 0.56, and further preferably not lower than 0.57. On the other hand, if the ratio is too large, the head 2 becomes heavy and it becomes difficult to swing the club. Therefore, the ratio is preferably not higher than 0.69, and further preferably not higher than 0.68.
- the material and structure of the grip 4 there is no particular limitation in the material and structure of the grip 4 , and those commonly used can be adopted as appropriate.
- those commonly used can be adopted as appropriate.
- the weight of the grip 4 itself is not particularly limited, it can be ordinarily set to be not smaller than 20 g but not larger than 55 g. If the weight of the grip 4 is too small, the strength of the grip 4 becomes low, and its durability may deteriorate. Therefore, the weight of the grip 4 is preferably not smaller than 23 g, and further preferably not smaller than 26 g. On the other hand, if the weight of the grip 4 is too large, the golf club 1 becomes heavy and difficult to swing. Therefore, the weight of the grip 4 is preferably not larger than 53 g, and further preferably not larger than 51 g.
- the shaft 3 in the present embodiment is a steel shaft having a hollow structure and is manufactured with a method commonly used in the art.
- the full length of the shaft 3 is represented as L S
- the distance from the tip end (front end) 3 a of the shaft 3 to the center of gravity G of the shaft 3 is represented as L G .
- a weight X of the shaft 3 in the present invention is set to be not smaller than 80 g but not larger than 140 g. If the weight of the shaft 3 is too small, the possibility becomes high for strengths such as flexural strength to be insufficient due to having a small thickness. Therefore, the weight of the shaft 3 is preferably not smaller than 85 g, and further preferably not smaller than 90 g. On the other hand, if the weight of the shaft 3 is larger than 140 g, it becomes difficult to perform a swing at an increased speed due to the whole golf club 1 being heavy. Therefore, the weight of the shaft 3 is preferably not larger than 135 g, and further preferably not larger than 130 g.
- the length (full length) L S of the shaft 3 is set to be not smaller than 30 inches but not larger than 42 inches. If the length of the shaft 3 is too small, a turning radius of the swing becomes small, and it becomes difficult to obtain a sufficient head speed. As a result, the ball speed cannot be increased, and the flight distance of the ball cannot be extended. Therefore, the length of the shaft 3 is preferably not smaller than 32 inches, and further preferably not smaller than 34 inches. On the other hand, if the length of the shaft 3 is too large, the inertia moment at the grip end becomes large, and a powerless golfer can become easily overwhelmed in terms of power. Therefore, the head speed cannot be increased, and the flight distance of the ball cannot be extended. Thus, the length of the shaft 3 is preferably not larger than 41.5 inches, and further preferably not larger than 41 inches.
- the position of the center of gravity itself of the shaft 3 is not particularly limited in the present invention, it is ordinarily within a range of, for example, for a shaft whose length is 39 inches, 595 to 505 mm from the tip end 3 a (front end) of the shaft 3 . If the position of the center of gravity G of the shaft 3 is located closer than 505 mm from the front end of the shaft 3 , there is a high possibility of not being able to increase head speed since the ease of swinging the club is not improved due to the position of the center of gravity not being sufficiently moved in the hand side direction.
- the position of the center of gravity of the shaft 3 from the front end of the shaft 3 is preferably not closer than 510 mm, and further preferably not closer than 515 mm.
- the position of the center of gravity G of the shaft 3 is farther than 595 mm from the front end of the shaft 3 , there is a high possibility of strengths such as flexural strength being insufficient due to a small thickness on the front end side of the shaft. Therefore, the position of the center of gravity of the shaft 3 from the front end of the shaft 3 is preferably not farther than 585 mm, and further preferably not farther than 575 mm.
- the center-of-gravity rate Y is lower than 51.0(%), since the center of gravity of the shaft is located close to the front end side of the shaft, the weight of the head has to be reduced in order to obtain a swing balance equivalent to that obtained from a hitherto known club, and the degree of freedom in designing a head becomes small. Thus, the inertia moment of the head becomes small, and a technique for lowering the center of gravity cannot be implemented. Therefore, it becomes difficult to achieve a large ball flight distance.
- the center-of-gravity rate Y is preferably not lower than 52.0, and further preferably not lower than 53.0.
- the center-of-gravity rate Y is higher than 60.0, since the center of gravity of the shaft is located too close to the back end side of the shaft, even if the weight of the head is excessively increased in order to obtain a level of ease of swinging equivalent to that obtained from a hitherto known club, i.e., the same level of swing balance; it is still difficult to perform a swing since the club weight is also increased.
- the weight is allocated on the back end side rather than on the front end of the shaft, the strength of the front end side of the shaft becomes small. Therefore, the center-of-gravity rate Y is preferably not higher than 58.0, and further preferably not higher than 56.0.
- a thickness t of a portion up to 150 mm from the butt end 3 b of the shaft 3 toward the front end side of the shaft is set to be not smaller than 0.30 mm but not larger than 0.40 mm.
- the thickness t is smaller than 0.3 mm, since the center of gravity of the shaft is located close to the front end side of the shaft, the weight of the head has to be reduced in order to obtain a swing balance equivalent to that obtained from a hitherto known club, and the degree of freedom in designing a head becomes small. Thus, the inertia moment of the head becomes small, and a technique for lowering the center of gravity cannot be implemented. Therefore, it becomes difficult to achieve a large ball flight distance.
- the thickness t is preferably not smaller than 0.32 mm, and further preferably not smaller than 0.34 mm.
- the thickness t is larger than 0.4 mm, since the center of gravity of the shaft is located too close to the back end side of the shaft, even if the weight of the head is excessively increased in order to obtain a level of ease of swinging equivalent to that obtained from a hitherto known club, i.e., the same level of swing balance; it is still difficult to perform a swing since the club weight is also increased.
- the thickness t is preferably not larger than 0.38 mm, and further preferably not larger than 0.36 mm.
- an outer diameter d of a portion up to 150 mm from the butt end 3 b of the shaft 3 toward the front end side of the shaft is set to be not smaller than 14.5 mm but not larger than 15.3 mm.
- the outer diameter d is smaller than 14.5 mm, a flexural rigidity value EI of the butt side of the shaft becomes too low and the shaft becomes soft.
- the outer diameter d is preferably not smaller than 14.7 mm, and further preferably not smaller than 14.9 mm.
- the outer diameter d is preferably not larger than 15.4 mm, and further preferably not larger than 15.3 mm.
- the number of steps included in a portion up to 400 mm from the butt end 3 b of the shaft 3 toward the front end side of the shaft is set to be not less than 5 but not more than 8.
- the number of the steps is less than 5, the flexural rigidity value EI of the butt side of the shaft becomes too high, and the feel obtained when hitting a ball deteriorates since the shaft bends little and is felt as being hard. Therefore, the number of the steps is preferably not less than 6.
- the number of the steps is more than 8, the flexural rigidity value EI of the butt side of the shaft becomes too low and the shaft becomes soft.
- the number of the steps is preferably not more than 7.
- the contained amount of retained austenite in the material of the shaft is set to be larger in a portion toward the butt end 3 b from this 600-mm part. That is, the contained amount of retained austenite is different in the tip end side of the shaft and in the butt end side of the shaft, with the boundary therebetween being the part 600 mm from the tip end 3 a of the shaft toward the butt end 3 b side. More specifically, the contained amount of retained austenite in the portion on the butt end side of the 600-mm boundary is set to be larger than the tip end side of the boundary.
- the “boundary” is located closer than 600 mm from the tip end 3 a of the shaft with respect to the butt end 3 b side, the flexural rigidity value EI of the butt side of the shaft becomes too low and the shaft becomes soft. In addition, since directional stability of a hit ball deteriorates, the feel obtained when hitting a ball deteriorates. Therefore, the “boundary” is located preferably not closer than 650 mm, and further preferably not closer than 700 mm.
- the “boundary” is located farther than 900 mm from the tip end 3 a of the shaft toward the butt end 3 b , the flexural rigidity value EI of the butt side of the shaft becomes too high, and the feel obtained when hitting a ball deteriorates since the shaft bends little and is felt as being hard. Therefore, the “boundary” is located preferably not farther than 850 mm, and further preferably not farther than 800 mm.
- FIG. 2 is an illustrative diagram for the method for measuring the SG-type three point flexural strength.
- load F was applied downward from above at a load point t 3 while the shaft 3 was supported from below at two support points t 1 and t 2 .
- the position of the load point t 3 was a position dividing, into two equal parts, the interval between the support point t 1 and the support point t 2 .
- the load point t 3 was matched with the point (T-point) that was to be measured, and measurement was conducted.
- Example 4 Example 5 Example 1 Example 6 Example 7 Shaft weight [g] 95 95 95 95 95 Shaft full length [inch] 38 38 38 38 38 38 Center-of-gravity rate [%] 55 55 55 55 55 Thickness [mm] of a portion 0.35 0.35 0.35 0.35 0.35 from butt end to 150 mm therefrom Outer diameter [mm] of a portion 14.4 14.7 15 15.3 15.6 from butt end to 150 mm therefrom Number of steps 5 5 5 5 5 Contained amount of retained austenite Uniform Uniform Uniform Uniform Feel evaluation 5 4 3 2 1 Flexural strength (T-point) [kgf] 220 220 220 220 220 of front end part Flight distance [yard] 162 165 170 165 162
- Example 1 Example 9
- Example 10 Example 11 Shaft weight [g] 95 95 95 95 95 Shaft full length [inch] 38 38 38 38 38 38 38 Center-of-gravity rate [%] 55 55 55 55 55 Thickness [mm] of a portion 0.35 0.35 0.35 0.35 0.35 from butt end to 150 mm therefrom Outer diameter [mm] of a portion 15 15 15 15 from butt end to 150 mm therefrom Number of steps 4 5 6 5 5 5 Contained amount of retained austenite Uniform Uniform Larger in Larger in tip end butt end side side Feel evaluation 2 3 4 2 4 Flexural strength (T-point) [kgf] 220 220 220 210 220 of front end part Flight distance [yard] 162 170 168 168 168
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Abstract
A golf club steel shaft in which, when a distance from a front end of the shaft to a center of gravity point of the shaft is LG and when a full length of the shaft is LS, a center-of-gravity rate Y (%) obtained as LG/LS satisfies 51.0≦Y≦60.0, a shaft weight X (g) satisfies 80≦X≦140, and a full length of the shaft LS (inch) satisfies 30≦LS≦42.
Description
- The present invention relates to a steel shaft.
- For golfers, flight distance of a ball is one of the important factors when selecting a golf club. Therefore, hitherto, in order to extend the flight distance of the ball, various improvements have been made with regard to shapes and materials of elements forming a golf club.
- However, in recent years, in order to enhance fairness of competition by suppressing excessive flight distance, there have been regulations set in the rules regarding rebound performance of a clubface, club length, and inertia moment of a head; and thereby it is becoming difficult to improve flight distance.
- In such a situation, in view of the fact that initial velocity of a ball largely influences flight distance, there has been a proposal (for example, cf. Patent Literature 1) of extending the club length close to the upper limit regulated by the rule to increase head speed of a club.
-
- [PTL1] Japanese Laid-Open Patent Publication No. 2004-201911
- However, with the method of increasing head speed of a club by extending the club length, controllability of the head deteriorates as the length of the club becomes longer, and it becomes difficult to hit a ball at a sweet spot of the head. Thus, a ball smash factor deteriorates and initial velocity of a ball cannot be stably increased; and, as a result, flight distance of a ball cannot be improved.
- In order to solve this, it is necessary to increase the smash factor by reducing the length of the club and increase initial velocity of the ball by increasing the head weight. However, simply increasing the head weight leads to a problem where ease of swinging the club decreases due to inertia moment of the club now becoming large.
- Therefore, it is conceivable to move the center of gravity of the shaft toward the butt side (hand side) in order to prevent the increase of inertia moment of the club without further increasing the club weight.
- Although it is ordinarily possible to move the center of gravity of the shaft toward the butt side by increasing the thickness of the a butt side portion of the shaft; with this method, a flexural rigidity value EI (kgf·m2) of the butt side portion of the shaft also increases, and feel of hitting a ball and directivity of a hit ball deteriorate.
- The present invention has been made in view of such circumstances, and an objective of the present invention is to provide a golf club steel shaft that makes it possible to extend flight distance of a ball while maintaining feel of hitting a ball and directivity of a hit ball.
- (1) In a golf club steel shaft of the present invention,
- when a distance from a front end of the shaft to a center of gravity point of the shaft is LG and when a full length of the shaft is LS, a center-of-gravity rate Y (%) obtained as LG/LS satisfies 51.0≦Y≦60.0,
- a shaft weight X (g) satisfies 80≦X≦140, and
- a full length of the shaft LS (inch) satisfies 30≦LS≦42.
- In the golf club steel shaft of the present invention, since the center-of-gravity rate Y (%), the shaft weight X (g), and the full length of the shaft LS (inch) are each set as values within the above described ranges, it is possible to increase weight of a golf club head with steel iron, and extend flight distance of a ball while maintaining feel of hitting a ball and directivity of a hit ball.
- (2) In the golf club steel shaft according to (1) described above, a thickness of a portion up to 150 mm from a butt end toward a front end side of the shaft is preferably not smaller than 0.30 mm but not larger than 0.40 mm.
- (3) In the golf club steel shaft according to (1) or (2) described above, an outer diameter of a portion up to 150 mm from a butt end toward a front end side of the shaft is preferably not smaller than 14.5 mm but not larger than 15.3 mm.
- (4) In the golf club steel shaft according to (1) to (3) described above, the number of steps included in a portion up to 400 mm from a butt end toward a front end side of the shaft is preferably not less than 5 but not more than 8.
- With the steel shaft according to the present invention, it is possible to extend flight distance of a ball while maintaining feel of hitting a ball and directivity of a hit ball.
-
FIG. 1 is an illustrative diagram of a golf club including one embodiment of a golf club steel shaft of the present invention. -
FIG. 2 is for describing a method for measuring T-point strength. - In the following, detailed embodiments of a steel shaft for a golf club of the present invention will be described with reference to the accompanying drawings.
-
FIG. 1 is an illustrative diagram showing the entirety of agolf club 1 including a steel shaft (hereinafter, may be simply referred to as “shaft”) for a golf club, according to one embodiment of the present invention. Thegolf club 1 includes an iron typegolf club head 2 having a predetermined loft angle, ashaft 3, and agrip 4. Thehead 2 has ahosel 6 including ashaft hole 5 to which atip end 3 a on the front end side of theshaft 3 is inserted and fixed. Abutt end 3 b at the back end side of theshaft 3 is inserted and fixed in a grip hole 7 of thegrip 4. Thetip end 3 a is positioned inside thehead 2, and thebutt end 3 b is positioned inside thegrip 4. It should be noted that, inFIG. 1 , a reference character of “G” indicates the center of gravity (center of gravity point) of theshaft 3. The center of gravity G is located on a shaft axis inside theshaft 3. - Although the weight of the
golf club 1 is not particularly limited in the present invention, it is preferably set within a range of not smaller than 360 g. If the weight of thegolf club 1 is too small, the strengths of respective elements (parts) forming thegolf club 1 become low, and durability of thegolf club 1 may deteriorate. Therefore, the weight of thegolf club 1 is preferably not smaller than 370 g, and further preferably not smaller than 380 g. On the other hand, if the weight of thegolf club 1 is too large, it becomes difficult to perform a swing, and it becomes difficult to increase head speed. Therefore, the weight of thegolf club 1 is further preferably not larger than 500 g, and particularly preferably not larger than 490 g. - Furthermore, the length of the
golf club 1 itself is also not particularly limited in the present invention, and is ordinarily from 34.0 to 42.0 inches. If the length of thegolf club 1 is too small, although a swing can be performed easily, a turning radius of the swing becomes small, and it becomes difficult to obtain a sufficient head speed. As a result, the ball speed cannot be increased, and the flight distance of the ball cannot be extended. Therefore, the length of thegolf club 1 is preferably not smaller than 34.5 inches, and further preferably not smaller than 35.0 inches. On the other hand, if the length of thegolf club 1 is too large, the head speed decreases since it becomes difficult to swing the club. Therefore, the ball speed cannot be increased, and the flight distance of the ball cannot be extended. Therefore, the length of thegolf club 1 is preferably not larger than 41.5 inches, and further preferably not larger than 41.0 inches. - It should be noted that, in the present specification, “club length” is a length measured based on the description in “Appendix II—Design of Clubs” “1. Clubs” “1c. Length” in the Rules of Golf determined by R&A (The Royal and Ancient Golf Club of Saint Andrews).
- [Head Configuration]
- The
head 2 in the present embodiment is a solid iron head and has a large inertia moment. With a club having thehead 2 with a large inertia moment, an advantageous effect of improvement in flight distance can be stably obtained. - In the present invention, there is no particular limitation in the material of the
head 2, and, for example, titanium, titanium alloys, stainless steel, maraging steel, soft iron, and the like can be used. Furthermore, instead of manufacturing thehead 2 using a single material, thehead 2 may be manufactured by combining multiple materials as appropriate. - In the present invention, although the weight of the
head 2 itself is not particularly limited, it is preferably within a range from 230 to 310 g. If thehead 2 is too light, the kinetic energy of thehead 2 cannot be sufficiently provided to the ball, and it becomes difficult to increase the ball speed. Therefore, the weight of thehead 2 is further preferably not smaller than 235 g, and particularly preferably not smaller than 240 g. On the other hand, if the weight of thehead 2 is too large, thegolf club 1 becomes heavy and difficult to swing. Therefore, the weight of thehead 2 is further preferably not larger than 305 g, and particularly preferably not larger than 300 g. - Furthermore, in the
golf club 1 of the present embodiment, the ratio (head weight/club weight) of the head weight and the club weight is set to be not lower than 0.55 but not higher than 0.70. If this ratio is too small, the kinetic energy of thehead 2 becomes small and obtaining a sufficient ball speed becomes difficult. Therefore, the ratio is preferably not lower than 0.56, and further preferably not lower than 0.57. On the other hand, if the ratio is too large, thehead 2 becomes heavy and it becomes difficult to swing the club. Therefore, the ratio is preferably not higher than 0.69, and further preferably not higher than 0.68. - [Grip Configuration]
- In the present invention, there is no particular limitation in the material and structure of the
grip 4, and those commonly used can be adopted as appropriate. For example, there can be used one that is obtained by blending and kneading natural rubber, oil, carbon black, sulfur, and zinc oxide, and molding and vulcanizing the materials into a predetermined shape. - In the present invention, although the weight of the
grip 4 itself is not particularly limited, it can be ordinarily set to be not smaller than 20 g but not larger than 55 g. If the weight of thegrip 4 is too small, the strength of thegrip 4 becomes low, and its durability may deteriorate. Therefore, the weight of thegrip 4 is preferably not smaller than 23 g, and further preferably not smaller than 26 g. On the other hand, if the weight of thegrip 4 is too large, thegolf club 1 becomes heavy and difficult to swing. Therefore, the weight of thegrip 4 is preferably not larger than 53 g, and further preferably not larger than 51 g. - [Shaft Configuration]
- The
shaft 3 in the present embodiment is a steel shaft having a hollow structure and is manufactured with a method commonly used in the art. The full length of theshaft 3 is represented as LS, and the distance from the tip end (front end) 3 a of theshaft 3 to the center of gravity G of theshaft 3 is represented as LG. - A weight X of the
shaft 3 in the present invention is set to be not smaller than 80 g but not larger than 140 g. If the weight of theshaft 3 is too small, the possibility becomes high for strengths such as flexural strength to be insufficient due to having a small thickness. Therefore, the weight of theshaft 3 is preferably not smaller than 85 g, and further preferably not smaller than 90 g. On the other hand, if the weight of theshaft 3 is larger than 140 g, it becomes difficult to perform a swing at an increased speed due to thewhole golf club 1 being heavy. Therefore, the weight of theshaft 3 is preferably not larger than 135 g, and further preferably not larger than 130 g. - In addition, the length (full length) LS of the
shaft 3 is set to be not smaller than 30 inches but not larger than 42 inches. If the length of theshaft 3 is too small, a turning radius of the swing becomes small, and it becomes difficult to obtain a sufficient head speed. As a result, the ball speed cannot be increased, and the flight distance of the ball cannot be extended. Therefore, the length of theshaft 3 is preferably not smaller than 32 inches, and further preferably not smaller than 34 inches. On the other hand, if the length of theshaft 3 is too large, the inertia moment at the grip end becomes large, and a powerless golfer can become easily overwhelmed in terms of power. Therefore, the head speed cannot be increased, and the flight distance of the ball cannot be extended. Thus, the length of theshaft 3 is preferably not larger than 41.5 inches, and further preferably not larger than 41 inches. - Furthermore, although the position of the center of gravity itself of the
shaft 3 is not particularly limited in the present invention, it is ordinarily within a range of, for example, for a shaft whose length is 39 inches, 595 to 505 mm from thetip end 3 a (front end) of theshaft 3. If the position of the center of gravity G of theshaft 3 is located closer than 505 mm from the front end of theshaft 3, there is a high possibility of not being able to increase head speed since the ease of swinging the club is not improved due to the position of the center of gravity not being sufficiently moved in the hand side direction. Therefore, the position of the center of gravity of theshaft 3 from the front end of theshaft 3 is preferably not closer than 510 mm, and further preferably not closer than 515 mm. On the other hand, if the position of the center of gravity G of theshaft 3 is farther than 595 mm from the front end of theshaft 3, there is a high possibility of strengths such as flexural strength being insufficient due to a small thickness on the front end side of the shaft. Therefore, the position of the center of gravity of theshaft 3 from the front end of theshaft 3 is preferably not farther than 585 mm, and further preferably not farther than 575 mm. - In the present invention, when the distance from the front end of the
shaft 3 to the center of gravity G of the shaft is LG and when the full length of theshaft 3 is LS, a center-of-gravity rate Y (%) obtained as LG/LS satisfies 51.0≦Y≦60.0. - If the center-of-gravity rate Y is lower than 51.0(%), since the center of gravity of the shaft is located close to the front end side of the shaft, the weight of the head has to be reduced in order to obtain a swing balance equivalent to that obtained from a hitherto known club, and the degree of freedom in designing a head becomes small. Thus, the inertia moment of the head becomes small, and a technique for lowering the center of gravity cannot be implemented. Therefore, it becomes difficult to achieve a large ball flight distance. Hence, the center-of-gravity rate Y is preferably not lower than 52.0, and further preferably not lower than 53.0.
- On the other hand, if the center-of-gravity rate Y is higher than 60.0, since the center of gravity of the shaft is located too close to the back end side of the shaft, even if the weight of the head is excessively increased in order to obtain a level of ease of swinging equivalent to that obtained from a hitherto known club, i.e., the same level of swing balance; it is still difficult to perform a swing since the club weight is also increased. In addition, since the weight is allocated on the back end side rather than on the front end of the shaft, the strength of the front end side of the shaft becomes small. Therefore, the center-of-gravity rate Y is preferably not higher than 58.0, and further preferably not higher than 56.0.
- Furthermore, in the present embodiment, a thickness t of a portion up to 150 mm from the
butt end 3 b of theshaft 3 toward the front end side of the shaft is set to be not smaller than 0.30 mm but not larger than 0.40 mm. - If the thickness t is smaller than 0.3 mm, since the center of gravity of the shaft is located close to the front end side of the shaft, the weight of the head has to be reduced in order to obtain a swing balance equivalent to that obtained from a hitherto known club, and the degree of freedom in designing a head becomes small. Thus, the inertia moment of the head becomes small, and a technique for lowering the center of gravity cannot be implemented. Therefore, it becomes difficult to achieve a large ball flight distance. Hence, the thickness t is preferably not smaller than 0.32 mm, and further preferably not smaller than 0.34 mm.
- On the other hand, when the thickness t is larger than 0.4 mm, since the center of gravity of the shaft is located too close to the back end side of the shaft, even if the weight of the head is excessively increased in order to obtain a level of ease of swinging equivalent to that obtained from a hitherto known club, i.e., the same level of swing balance; it is still difficult to perform a swing since the club weight is also increased. In addition, since the weight is allocated on the back end side rather than on the front end of the shaft, the strength of the front end side of the shaft becomes small. Therefore, the thickness t is preferably not larger than 0.38 mm, and further preferably not larger than 0.36 mm.
- Furthermore, in the present embodiment, an outer diameter d of a portion up to 150 mm from the
butt end 3 b of theshaft 3 toward the front end side of the shaft is set to be not smaller than 14.5 mm but not larger than 15.3 mm. - If the outer diameter d is smaller than 14.5 mm, a flexural rigidity value EI of the butt side of the shaft becomes too low and the shaft becomes soft. In addition, since directional stability of a hit ball deteriorates, the feel obtained when hitting a ball deteriorates. Therefore, the outer diameter d is preferably not smaller than 14.7 mm, and further preferably not smaller than 14.9 mm.
- On the other hand, if the outer diameter d is larger than 15.5 mm, the flexural rigidity value EI of the butt side of the shaft becomes too high, and the feel obtained when hitting a ball deteriorates since the shaft bends little and is felt as being hard. Therefore, the outer diameter d is preferably not larger than 15.4 mm, and further preferably not larger than 15.3 mm.
- Furthermore, in the present embodiment, the number of steps included in a portion up to 400 mm from the
butt end 3 b of theshaft 3 toward the front end side of the shaft is set to be not less than 5 but not more than 8. - If the number of the steps is less than 5, the flexural rigidity value EI of the butt side of the shaft becomes too high, and the feel obtained when hitting a ball deteriorates since the shaft bends little and is felt as being hard. Therefore, the number of the steps is preferably not less than 6.
- On the other hand, if the number of the steps is more than 8, the flexural rigidity value EI of the butt side of the shaft becomes too low and the shaft becomes soft. In addition, since directional stability of a hit ball deteriorates, the feel obtained when hitting a ball deteriorates. Therefore, the number of the steps is preferably not more than 7.
- In addition, in the present embodiment, when compared to a portion up to 600 mm from the
tip end 3 a of the shaft toward thebutt end 3 b side, the contained amount of retained austenite in the material of the shaft is set to be larger in a portion toward thebutt end 3 b from this 600-mm part. That is, the contained amount of retained austenite is different in the tip end side of the shaft and in the butt end side of the shaft, with the boundary therebetween being the part 600 mm from thetip end 3 a of the shaft toward thebutt end 3 b side. More specifically, the contained amount of retained austenite in the portion on the butt end side of the 600-mm boundary is set to be larger than the tip end side of the boundary. - If the “boundary” is located closer than 600 mm from the
tip end 3 a of the shaft with respect to thebutt end 3 b side, the flexural rigidity value EI of the butt side of the shaft becomes too low and the shaft becomes soft. In addition, since directional stability of a hit ball deteriorates, the feel obtained when hitting a ball deteriorates. Therefore, the “boundary” is located preferably not closer than 650 mm, and further preferably not closer than 700 mm. - On the other hand, if the “boundary” is located farther than 900 mm from the
tip end 3 a of the shaft toward thebutt end 3 b, the flexural rigidity value EI of the butt side of the shaft becomes too high, and the feel obtained when hitting a ball deteriorates since the shaft bends little and is felt as being hard. Therefore, the “boundary” is located preferably not farther than 850 mm, and further preferably not farther than 800 mm. - Next, the steel shaft of the present invention will be described based on Examples; however, the present invention is not limited only to those Examples.
- 15 golfers having an average head speed of 42 m/s were each asked to actually hit ten balls by using a 5-iron (club length: 38 inches, club weight: 400 g) having a shaft with a specification shown in Table 1, and were asked to answer a question regarding the feel obtained when hitting a ball. The golfers were asked to take into consideration ease of swinging, directivity of a hit ball, and flight distance to perform a 5-scale evaluation. An evaluation obtained from the most number of golfers was adopted.
- 5 points: Very good
- 4 points: Good
- 3 points: Average
- 2 points: Bad
- 1 point: Very bad
- A shaft front end strength (T-point strength) was measured in accordance with a testing method defined by SG mark. SG-type three point flexural strength is a SG-type breaking strength determined by the Consumer Product Safety Association.
FIG. 2 is an illustrative diagram for the method for measuring the SG-type three point flexural strength. As shown inFIG. 2 , load F was applied downward from above at a load point t3 while theshaft 3 was supported from below at two support points t1 and t2. The position of the load point t3 was a position dividing, into two equal parts, the interval between the support point t1 and the support point t2. The load point t3 was matched with the point (T-point) that was to be measured, and measurement was conducted. - Results of evaluation of feel of hitting a ball, flexural strength of a shaft front end portion, and flight distance are shown in Tables 1 to 3.
-
TABLE 1 Comparative Comparative Example 1 Example 2 Example 1 Example 3 Example 2 Shaft weight [g] 95 95 95 95 95 Shaft full length [inch] 38 38 38 38 38 Center-of-gravity rate [%] 49 52 55 58 61 Thickness [mm] of a portion 0.28 0.32 0.35 0.38 0.41 from butt end to 150 mm therefrom Outer diameter [mm] of a portion 15 15 15 15 15 from butt end to 150 mm therefrom Number of steps 5 5 5 5 5 Contained amount of retained austenite Uniform Uniform Uniform Uniform Uniform Feel evaluation 1 2 3 4 5 Flexural strength (T-point) [kgf] 240 230 220 190 160 of front end part Flight distance [yard] 162 167 170 168 160 -
TABLE 2 Example 4 Example 5 Example 1 Example 6 Example 7 Shaft weight [g] 95 95 95 95 95 Shaft full length [inch] 38 38 38 38 38 Center-of-gravity rate [%] 55 55 55 55 55 Thickness [mm] of a portion 0.35 0.35 0.35 0.35 0.35 from butt end to 150 mm therefrom Outer diameter [mm] of a portion 14.4 14.7 15 15.3 15.6 from butt end to 150 mm therefrom Number of steps 5 5 5 5 5 Contained amount of retained austenite Uniform Uniform Uniform Uniform Uniform Feel evaluation 5 4 3 2 1 Flexural strength (T-point) [kgf] 220 220 220 220 220 of front end part Flight distance [yard] 162 165 170 165 162 -
TABLE 3 Example 8 Example 1 Example 9 Example 10 Example 11 Shaft weight [g] 95 95 95 95 95 Shaft full length [inch] 38 38 38 38 38 Center-of-gravity rate [%] 55 55 55 55 55 Thickness [mm] of a portion 0.35 0.35 0.35 0.35 0.35 from butt end to 150 mm therefrom Outer diameter [mm] of a portion 15 15 15 15 15 from butt end to 150 mm therefrom Number of steps 4 5 6 5 5 Contained amount of retained austenite Uniform Uniform Uniform Larger in Larger in tip end butt end side side Feel evaluation 2 3 4 2 4 Flexural strength (T-point) [kgf] 220 220 220 210 220 of front end part Flight distance [yard] 162 170 168 168 168 -
-
- 1 iron type golf club
- 2 head
- 3 shaft
- 3 a tip end
- 3 b butt end
- 4 grip
- 5 shaft hole
- 6 hosel
- 7 grip hole
- G center of gravity of a shaft
- LG distance from a tip end of a shaft to the center of gravity of the shaft
- LS shaft full length
Claims (8)
1. A golf club steel shaft in which, when a distance from a front end of the shaft to a center of gravity point of the shaft is LG and when a full length of the shaft is LS, a center-of-gravity rate Y (%) obtained as LG/LS satisfies 51.0≦Y≦60.0, a shaft weight X (g) satisfies 80≦X≦140, and a full length of the shaft LS (inch) satisfies 30≦LS≦42.
2. The golf club steel shaft according to claim 1 , wherein a thickness of a portion up to 150 mm from a butt end toward a front end side of the shaft is not smaller than 0.30 mm but not larger than 0.40 mm.
3. The golf club steel shaft according to claim 1 , wherein an outer diameter of a portion up to 150 mm from a butt end toward a front end side of the shaft is not smaller than 14.5 mm but not larger than 15.3 mm.
4. The golf club steel shaft according to claim 2 , wherein an outer diameter of a portion up to 150 mm from a butt end toward a front end side of the shaft is not smaller than 14.5 mm but not larger than 15.3 mm.
5. The golf club steel shaft according to claim 1 , wherein the number of steps included in a portion up to 400 mm from a butt end toward a front end side of the shaft is not less than 5 but not more than 8.
6. The golf club steel shaft according to claim 2 , wherein the number of steps included in a portion up to 400 mm from a butt end toward a front end side of the shaft is not less than 5 but not more than 8.
7. The golf club steel shaft according to claim 3 , wherein the number of steps included in a portion up to 400 mm from a butt end toward a front end side of the shaft is not less than 5 but not more than 8.
8. The golf club steel shaft according to claim 4 , wherein the number of steps included in a portion up to 400 mm from a butt end toward a front end side of the shaft is not less than 5 but not more than 8.
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP2012-125139 | 2012-05-31 | ||
JP2012125139A JP2013248165A (en) | 2012-05-31 | 2012-05-31 | Steel shaft for golf club |
Publications (1)
Publication Number | Publication Date |
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US20130324289A1 true US20130324289A1 (en) | 2013-12-05 |
Family
ID=49670924
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
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US13/905,311 Abandoned US20130324289A1 (en) | 2012-05-31 | 2013-05-30 | Golf club steel shaft |
Country Status (4)
Country | Link |
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US (1) | US20130324289A1 (en) |
JP (1) | JP2013248165A (en) |
KR (1) | KR101450455B1 (en) |
CN (1) | CN103446734A (en) |
Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US20160250529A1 (en) * | 2015-02-26 | 2016-09-01 | Acushnet Company | Golf club with improved weighting |
US9616298B1 (en) | 2015-09-24 | 2017-04-11 | Acushnet Company | Golf club with improved weighting |
Families Citing this family (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US9119994B2 (en) * | 2012-12-03 | 2015-09-01 | Dunlop Sports Co. Ltd. | Golf club |
JP5546701B1 (en) * | 2013-07-22 | 2014-07-09 | ダンロップスポーツ株式会社 | Golf club |
JP5546700B1 (en) * | 2013-07-23 | 2014-07-09 | ダンロップスポーツ株式会社 | Golf club |
JP5546672B1 (en) * | 2013-09-20 | 2014-07-09 | ダンロップスポーツ株式会社 | Golf club |
JP5546673B1 (en) * | 2013-09-20 | 2014-07-09 | ダンロップスポーツ株式会社 | Golf club |
JP5886392B1 (en) * | 2014-09-10 | 2016-03-16 | ダンロップスポーツ株式会社 | Golf club |
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US6984179B2 (en) * | 2002-10-28 | 2006-01-10 | Royal Precision, Inc. | Golf club shafts having variable taper lengths |
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US20120071266A1 (en) * | 2008-08-12 | 2012-03-22 | Rice Scott A | Golf club shaft with high balance point and golf club including same |
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JPS6215368U (en) * | 1985-07-09 | 1987-01-29 | ||
JPH0657274B2 (en) * | 1987-08-13 | 1994-08-03 | 株式会社横尾製作所 | Method for manufacturing golf club shaft |
CA2013994A1 (en) * | 1989-04-10 | 1990-10-10 | Frank Fenton | Lightweight steel golf shaft |
JPH04317672A (en) * | 1991-04-16 | 1992-11-09 | Sumitomo Rubber Ind Ltd | Golf club shaft |
WO1998023338A1 (en) * | 1996-11-28 | 1998-06-04 | Wavex Corporation | Golf club shaft having wave shaped reinforced part |
JPH11267249A (en) * | 1998-03-19 | 1999-10-05 | Daiwa Seiko Inc | Golf club set |
JP2001037921A (en) * | 1999-05-24 | 2001-02-13 | Yokohama Rubber Co Ltd:The | Iron golf club set |
JP2002052105A (en) * | 2000-08-09 | 2002-02-19 | Yokohama Rubber Co Ltd:The | Golf club |
JP2002102400A (en) * | 2000-10-02 | 2002-04-09 | Nippon Shaft Co Ltd | Steel shaft |
JP2003102884A (en) * | 2001-09-28 | 2003-04-08 | Sumitomo Rubber Ind Ltd | Golf club shaft and method for manufacturing golf club shaft |
JP2004081344A (en) * | 2002-08-23 | 2004-03-18 | Sumitomo Rubber Ind Ltd | Golf club |
JP2004201911A (en) * | 2002-12-25 | 2004-07-22 | Yamaha Corp | Golf club |
JP2007130087A (en) * | 2005-11-08 | 2007-05-31 | Bridgestone Sports Co Ltd | Golf club |
-
2012
- 2012-05-31 JP JP2012125139A patent/JP2013248165A/en active Pending
-
2013
- 2013-05-22 KR KR1020130057612A patent/KR101450455B1/en active IP Right Grant
- 2013-05-30 US US13/905,311 patent/US20130324289A1/en not_active Abandoned
- 2013-05-31 CN CN2013102111767A patent/CN103446734A/en active Pending
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US5022652A (en) * | 1989-04-10 | 1991-06-11 | Spalding & Evenflo Companies | Lightweight steel golf shaft |
US6984179B2 (en) * | 2002-10-28 | 2006-01-10 | Royal Precision, Inc. | Golf club shafts having variable taper lengths |
US7048645B2 (en) * | 2002-11-20 | 2006-05-23 | Sri Sports Limited | Golf club shaft |
US20080242438A1 (en) * | 2007-03-29 | 2008-10-02 | Nhk Spring Co., Ltd. | Golf shaft, golf club, and production method for golf shaft |
US20120071266A1 (en) * | 2008-08-12 | 2012-03-22 | Rice Scott A | Golf club shaft with high balance point and golf club including same |
Cited By (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US20160250529A1 (en) * | 2015-02-26 | 2016-09-01 | Acushnet Company | Golf club with improved weighting |
US9616298B1 (en) | 2015-09-24 | 2017-04-11 | Acushnet Company | Golf club with improved weighting |
US10046216B2 (en) | 2015-09-24 | 2018-08-14 | Acushnet Company | Golf club with improved weighting |
US10391373B2 (en) | 2015-09-24 | 2019-08-27 | Acushnet Company | Golf club with improved weighting |
Also Published As
Publication number | Publication date |
---|---|
CN103446734A (en) | 2013-12-18 |
KR101450455B1 (en) | 2014-10-13 |
JP2013248165A (en) | 2013-12-12 |
KR20130135080A (en) | 2013-12-10 |
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