Patent Application
20090253531
This nonprovisional application is based on Japanese Patent Application No. 2008-093428 filed on Mar. 31, 2008 with the Japan Patent Office, and No. 2009-059146 filed on Mar. 12, 2009, the entire contents of which are hereby incorporated by reference.
1. Field of the Invention
The present invention relates to golf club and its manufacturing method and, more specifically, to a golf club having a face portion and a neck portion formed integrally, as well as to the method of manufacturing the same.
2. Description of the Background Art
Generally, a head portion of a golf club includes a face portion having a ball-hitting surface and a neck portion connecting the face portion to a shaft. Conventionally, when a golf club head is formed by forging, the face and neck portions are formed integrally as one piece. The resulting head, however, has a disadvantage that the neck portion tends to deform at the time of hitting. Therefore, the neck portion must be made thick, and it has been difficult to reduce mass distribution to the neck portion. Alternatively, the face portion and the neck portion may be formed through different manufacturing steps and thereafter joined to each other. In that case, strength at the joint portion between the face and neck portions is inevitably low.
As a solution to such problems, International Publication WO01/056666 proposes a golf club.
In the golf club described in the pamphlet of WO01/056666 mentioned above, however, distribution of grain flows in the face portion is uneven, so that strength and toughness undesirably vary position to position at the face portion and, because of this, it has been difficult to attain satisfactory hitting feeling when one hits the ball with a conventional golf club.
The present invention was made in view of the foregoing, and its object is to provide a golf club that attains satisfactory hitting feeling by realizing uniform distribution of grain flows in the golf head, as well as to provide a method of manufacturing the same.
The present invention provides a golf club, including a golf head including a face portion with a ball hitting surface and a neck portion connecting the face portion to a shaft; wherein grain flows are formed in the golf head, and density of the grain flows inside the golf head is made comparable to density of the grain flows at a surface layer portion of the golf head.
The method of manufacturing the golf club in accordance with the present invention includes the drawing step of drawing a bar-shaped member to reduce diameter of the bar-shaped member; the reducing step of reducing diameter of one end of the bar-shaped member that has been drawn at the drawing step, to be smaller than the diameter of the other end; the bending step of bending the bar-shaped member; and the forging step, following the bending step, of forging the bar-shaped member to integrally form the face portion and the neck portion.
Preferably, the drawing step includes the step of hardening at least a part of circumferential surface of the bar-shaped member, while retaining grain flows.
Preferably, the forging step includes a first forging step of performing a plurality of coarse forging steps on the bar-shaped member to bring the bar-shaped member closer to a final shape while retaining grain flows, and a second forging step of performing fine forging process on a body resulting from the coarse forging steps, to attain the final shape.
In the golf club in accordance with the present invention, substantially uniform distribution of grain flows can be attained in the golf head, and satisfactory hitting feeling can be attained. By the method of manufacturing a golf club in accordance with the present invention, a golf club having grain flows distributed substantially uniformly in the golf club head can be obtained.
The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.
The golf club and its manufacturing method in accordance with the present invention will be described with reference to
Most of the grain flows 13 extend continuously from neck portion 12 to face portion 11 and, at face portion 11, grain flows 13 extend continuously in one direction.
In face portion 11, grain flows 13 extend from a connecting portion to neck portion 12 to a toe portion 14. As the grain flows 13 continuously extend from neck portion 12 to face portion 11, strength at the connecting portion between face portion 11 and neck portion 12 can be improved.
Distribution density of grain flows 13 at the ball hitting surface 15 of face portion 11 is comparable to the distribution density of grain flows 13 inside the face portion 11. Specifically, at face portion 11, grain flows are distributed substantially uniformly from the side of ball hitting surface 15 to the side of a rear surface 16.
Here, strength and toughness of head 10 of the golf club in accordance with the present embodiment are made uniform, possibly because of uniform distribution of grain flows 13 in head 10.
Observation revealed that the crystal structure of face portion 11 was not a layered structure, and that the metal was well hardened. It can be seen from this that hardness of face portion 11 has also been improved.
Referring to
Then, as shown in
By the hardening of bar-shaped member 21, the diameter of bar-shaped member 21 can be reduced while maintaining grain flows 13, whereby bar-shaped member 20 is formed.
As shown in
By such plastic working on one side of bar-shaped member 20, cross-sectional area of the said one side is made smaller and hence, density of grain flows 13 on the one side of bar-shaped member 20 can be increased as shown in
Neck body 12 is formed on this end, and face body 11 is formed on the other end. Consequently, it is expected that density of grain flows 13 at the neck body 20 can be increased to be higher than the density of grain flows 13 at the face body 11, as shown in
A process other than the drawing process described above may be adopted, provided that the cross-sectional area of bar-shaped member 20 can be reduced by plastic deformation of one end of bar-shaped member 20.
Next, as shown in
In the coarse forging process, the bar-shaped member 20 is subjected to stepwise plastic deformation, so that it becomes possible to retain substantially perfect grain flows 13 in the material as shown in
Further, by the three steps of coarse forging, deformation to almost finished shape can be attained as shown in
Next, after trimming, the fine forging process is performed as the finishing process, and details such as score lines are formed, as shown in
For the golf club of comparative example, a bar-shaped carbon steel that originally has the diameter of about 27 mm is used, on which the drawing process of the method of manufacturing a golf club in accordance with the present embodiment is not performed.
The golf club as the comparative example is formed by performing area-reducing process on an end portion of carbon steel, three steps of coarse forging, and fine forging.
Here, as shown in
On the other hand, as shown in
Thus, it can be understood that in the golf club in accordance with the present embodiment, grain flows 13 are distributed with higher uniformity than in the golf club as the comparative example. Further, in the golf club in accordance with the present embodiment, density of grain flows 13 inside the face portion 11 is higher than in the golf club as the comparative example.
As shown in
On the other hand, as shown in
As described above, in neck portion 12 of the golf club in accordance with the present embodiment, grain flows 13 are formed more uniformly from the surface layer side to the central portion, than in the neck portion 12 of comparative example.
Further, it can be seen that the density of grain flows 13 formed at the neck portion 12 of golf club in accordance with the present embodiment is higher than the density of grain flows 13 formed at the neck portion 12 of the golf club of comparative example.
In
Points of measurement are as shown in
Here, it can be seen that at points P2, P3, P6, P7, P11 and P12 positioned inside the golf club, the difference in hardness between the golf club of the present embodiment and that of comparative example is significantly large.
Particularly, at the hosel, the difference in hardness is as large as about 20 (Hv).
Possible reason why the hardness is improved in the golf club of the present embodiment than in the comparative example is that distribution density of grain flows is higher in the golf club of the present embodiment than in the golf club of comparative example, and that the distribution is more uniform.
As the hardness of golf club head 10 can be improved, strength can also be improved and, therefore, thickness of face portion 11 and head 10 can be reduced.
That the face portion 11 and head portion 10 can be made thinner enables more flexible weight design of head 10.
Specifically, it is possible to arrange the center of gravity of head 10 to a lower back side to enlarge a sweet area, or to design the weight balance of head 10 such that the sweet spot is positioned closer to the meet point. The sweet spot refers to an intersection of a face surface and a line extended vertically downward to the face surface from the center of gravity of an iron head.
Trial was performed by ten players using the golf club in accordance with the present embodiment and the golf club of the comparative example (Comparative Example), and eight of the players expressed “good hitting feeling.” Table 1 shows the result.
Here, HC represents handicap, and H/S represents head speed. “Fade” refers to a ball that once goes to the left side of ball flying line and then curves to the right, while “draw” refers to a ball that once goes to the right side of ball flying line and then curves to the left.
As described above, it can be understood that the golf club in accordance with the present embodiment attains good hitting feeling.
Through intensive study, the inventors found that, in short, the hitting feeling substantially depends on hitting sound. Specifically, while the players of trial shown in Table 1 express good hitting feeling in various phrases, the good feeling comes from good hitting sound. Particularly, the player feels good when the hitting sound has relatively low frequency and long reverberation, leaving comfortable echo.
As shown in
The sound in area P2 surrounded by the dotted line derives from the sound of head swooshing through the air and the frictional sound of golf club head touching the ground, and it is not directly related to the ball hitting sound. On the other hand, the sound in area P1 surrounded by the solid line represents the hitting sound of golf club head hitting the ball.
The sound in area P1 surrounded by the solid line is distributed in a range of relatively low frequency, and it can be seen that the sound lingers for a while.
It can be understood from above that the hitting sound when a ball is hit by the golf club in accordance with the present embodiment has relatively low frequency and lingers long with echo, which leads to the result of Table 1 that good hitting feeling is attained by the golf club in accordance with the present embodiment.
Though the present invention has been applied to an iron club in the embodiment above, the idea of the present invention is also applicable to a wood club face.
Although the present invention has been described and illustrated in detail, it is clearly understood that the same is by way of illustration and example only and is not to be taken by way of limitation, the scope of the present invention being interpreted by the terms of the appended claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2008-093428 | Mar 2008 | JP | national |
| 2009-059146 | Mar 2009 | JP | national |
