Games using tangible projectile – Golf – Club or club support
Reexamination Certificate
1999-04-20
2004-08-10
Blau, Stephen (Department: 3711)
Games using tangible projectile
Golf
Club or club support
Reexamination Certificate
active
06773358
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to an anisotropic golf club shaft and more particularly to a method of improving the strength of the anisotropic golf club shaft and enhancing productivity thereof.
DESCRIPTION OF THE RELATED ART
Needless to say, it is advantageous to hit a golf ball straight to get a good score and fly it a long distance. However, many golfers puzzle over the fact that golf balls hit are likely to be curved, i.e., they fly a so-called hook ball or a slice ball.
The golf ball is curved because the orientation of the orbit of a club head and the orientation (orientation of line normal to face of club head) of the face of the club head are not coincident with each other at an impact time. That is, when the face (orientation of line normal to face of the club head) of the club head is directed to the right with respect to the orbit of the club head, the golf ball is curved to the right (slice in the case of right-handed player), whereas when the face of the club head is directed to the left with respect to the orbit of the club head, the golf ball is curved to the left (slice in the case of right-handed player).
Thus, to fly the golf ball straight to an aimed direction, it is necessary to correct the orientation of the face of the club head at an impact time. But it is not easy to correct a swinging form. Thus, many players puzzle over how to correct their swinging forms.
In Japanese Laid-Open Patent Publication No. 3-227616, the present applicant describes that in a hollow or solid shaft having an anisotropic material such as fiber reinforced resin or the like formed at at least one part of the shaft, a fibrous angle of the anisotropic material is differentiated (varied) partly in a circumferential direction of the shaft and at at least one part of the shaft in the thickness direction thereof to differentiate the principal elastic axis of the shaft from the principal geometric axis. In this manner, the principal elastic axis can set at an arbitrary position.
In the hollow shaft in which the principal elastic axis is differentiated from the principal geometric axis to set it at an arbitrary position, when a load is so applied downward to the shaft that the load does not pass through a point located on the principal elastic axis, the hollow shaft is flexed and twisted, as shown in
FIGS. 15 and 16
. That is, as shown in
FIG. 15
, supposing that one end of a hollow shaft
10
is denoted by a fixed end
10
c
and that the other end thereof is denoted by a free end
10
d
, a principal elastic axis E is not coincident with a principal geometric axis G, and the free end 10d is positioned upward from a point Q located on the principal elastic axis E. When a load W not passing through the point Q located on the principal elastic axis E is applied to the free end
10
d
of the shaft
10
, the shaft
10
is flexed and twisted, as shown in FIG.
16
.
Further, the present applicant proposed a golf club to which a hollow shaft having the above-described anisotropic property is applied, as disclosed in Japanese Laid-Open. Patent Publication No. 10-328338. According to the disclosure made therein, the shaft is twisted by the flexure thereof when the golf club is swung so that when a hooker or a slicer uses the golf club, the orientation (orientation of line normal to face of club head) of the face of the club head is self-corrected. In the golf club, the club head is installed on the end of the anisotropic shaft which is flexed and twisted such that a line normal to the face of the club head is oriented to the direction in which a golf ball is to be flied, i.e., the face of the club head is oriented to a specific direction owing to twisting of the shaft at a desired angle caused by flexure thereof which occurs when the golf club is swung.
In the above Japanese Laid-Open Patent Publication No. 10-328338, an anisotropic shaft is manufactured by winding on a mandrel (a molding core rod) a semi-circumference prepreg in a region of 0°≦&thgr;<180° (first semi-circumference region) and in a region of 180°≦&thgr;360° (second semi-circumference region) in the circumferential direction of the shaft, respectively such that reinforcing fibers of both prepregs incline in opposite directions with respect to the axial direction of the shaft. A plurality of layers each consisting of two semi-circumference prepregs inclining in opposite directions is wound on the mandrel to produce the anisotropic shaft. According to this method, an uncontinuous portion of the reinforcing fibers is formed in the boundary between the first semi-circumference region and the second semi-circumference region. Thus, the strength of the shaft is low at the uncontinuous portion. Further, two semi-circumference prepregs are used to form one layer. Thus, it takes long to manufacture the golf club shaft and further, there may be a variation in the characteristics of products. To solve the problems, the present applicant proposed a golf club shaft and a method of manufacturing the golf club shaft, as disclosed in Japanese Laid-Open Patent Publication No. 11-76480.
In the golf club shaft and the method of manufacturing the golf club shaft, a hoop layer whose reinforcing fibers are substantially perpendicular to the axial direction of the shaft is layered on the boundary (uncontinuous portion of reinforcing fiber) between the first semi-circumference region consisting of one semi-circumference prepreg whose reinforcing fibers incline in one direction and the second semi-circumference region consisting of the other semi-circumference prepreg whose reinforcing fibers incline in the opposite direction. This is to prevent deterioration of the strength of the boundary therebetween. The two semi-circumference prepregs whose reinforcing fibers incline in opposite directions are bonded to the hoop layer to prepare a composite prepreg sheet in advance. The composite prepreg sheet is wound on the peripheral surface of the mandrel to manufacture the golf club shaft, thereby a period of time of manufacturing can be short and a degree of variation in the characteristics of products can be reduced.
However, in the proposal disclosed in Japanese Laid-Open Patent Publication No. 11-76480, it is possible to allow the strength and productivity of the shaft to be higher than those of the shaft not provided with the hoop layer. But the shaft has a seam (boundary between two semi-circumference prepregs) present in each layer, namely, in one turn of each layer consisting of the first and second semi-circumference prepregs. Thus, the strength of the shaft is still low.
It is ideal that the edges of the two prepregs are butted each other at the seam without forming a gap therebetween and overlapping them on each other. But it is difficult to butt them each other in such an ideal state in factories because they are operated for a mass production. Thus, there is necessarily a variation in the finish of the seam. In other words, in order to accomplish such an ideal butting of the prepregs, it is necessary for skilled operators to work without sparing any effort and time, which lowers the productivity of the shaft greatly. The above-described gap between the two prepregs and the overlapping thereof are defects of the shaft in its construction. Thus, in much consideration of the durability of the shaft, namely, such a defect cannot be ignored.
In the case of the conventional shaft (principal elastic axis and principal geometric axis are coincident with each other), in order to allow the shaft to have a uniform property in its circumferential direction, a prepreg is wound by at least one turn, without changing the material thereof. In the case of the anisotropic shaft, the semi-circumference prepreg is used. Thus, when the same amount of prepreg is used to manufacture the anisotropic shaft and the conventional shaft, the total number of prepregs to be used in the former is more than that of prepregs to be used in the latter. Further, in the case of the anisotropic shaft, it is necessary to butt two prepregs each other for each cir
Onuki Masahide
Sumitomo Norio
Blau Stephen
Sumitomo Rubber Industries., LTD
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