Games using tangible projectile – Golf – Club or club support
Reexamination Certificate
1999-08-06
2003-03-18
Wong, Steven (Department: 3711)
Games using tangible projectile
Golf
Club or club support
C473S319000
Reexamination Certificate
active
06533677
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
Generally, the present invention relates to a golf club shaft and more particularly to an anisotropic golf club shaft which has an improved strength, is produced with a high productivity, and is lightweight.
2. Description of the Related Art
Needless to say, it is advantageous to hit a golf ball straight to get a good score and hit it a long distance. However, many golfers puzzle over the fact that golf balls they hit are likely to be curved, i.e., they hit a so-called hook ball or a so-called 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 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 (hook in the case of right-handed player).
Thus, to hit 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. HEI3-227616, 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, it is possible to differentiate the principal elastic axis of the shaft from the principal geometric axis by differentiating (varying) a fibrous angle of the anisotropic material partly in the circumferential direction of the shaft and at at least one part of the shaft in the thickness direction thereof. 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, 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. 10 and 11
. That is, as shown in
FIG. 10
, supposing that one end of a hollow shaft
10
is denoted by
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
10
d
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.
11
.
The present applicant proposed a golf club to which a hollow shaft having the above-described anisotropic property is applied, as disclosed in Japanese Patent Application No. HEI9- 146950. 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 front 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 Patent Application No. HEI9- 146950, an anisotropic shaft is manufactured by winding on a mandrel a semicircumference-long prepreg in a region of 0°≦&thgr;<180° (first semi-circumference region) and in a region of 180°≦&thgr;<360° (second semicircumference 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 one circumference-long layers each consisting of two semicircumference-long prepregs inclining in opposite directions with respect to the axial direction of the shaft is wound one upon another on the mandrel to produce the anisotropic shaft. According to this method, an uncontinuous portion (seam of prepregs: dividing line) of the reinforcing fibers is formed in the boundary between the first and second semicircumference regions of the prepreg corresponding to one circumference of the shaft. Thus, the strength of the shaft is low at the uncontinuous portion. Further, two semicircumference-long prepregs are wound per one circumference of the shaft. Thus, it takes long to manufacture the golf club shaft and further, there may be a variation in the characteristics of products.
In Japanese Laid-Open Patent Publication No. HEI10-71220, there is proposed a golf club shaft which is flexed and twisted (flexed and twisted around the axis) similarly to the golf club shaft disclosed in Japanese Patent Application No. HEI9-146950. According to the disclosure, a shaft is divided into two circular-arcs in a cross-sectional face of the shaft to divide the shaft into two regions along the longitudinal direction (axial direction) of the shaft; and semicircumference-long prepregs are layered one upon another in the two regions such that the fibrous direction, amount of fiber, and resin impregnation amount of a prepreg positioned in one region are different from those of a prepreg positioned in the other region. However, because the semicircumference-long prepregs are layered one upon another in the two regions partitioned along the longitudinal direction (axial direction) of the shaft, an uncontinuous portion (seam of prepregs: dividing line) of the reinforcing fiber is formed in the boundary between the first and second semicircumference regions of the prepreg corresponding to one circumference of the shaft. Consequently, there is a variation in the characteristics of products.
The present applicant proposed a golf club shaft and a method of manufacturing the golf club shaft, as disclosed in Japanese Patent Application No. HEI9-242340 to solve the disadvantage of the anisotropic shaft in which the dividing line is formed on the cross-sectional face of the shaft because two semicircumference-long prepregs are wound per one circumference of the shaft.
In the golf club shaft and the method of manufacturing the golf club shaft, a hoop layer whose reinforcing fiber is substantially perpendicular to the axial direction of the shaft is layered one upon another on the boundary (uncontinuous portion of reinforcing fibers) between the first semicircumference region consisting of one semicircumference-long prepreg whose reinforcing fiber inclines in one direction and the second semicircumference region consisting of the other semicircumference-long prepreg whose reinforcing fiber inclines in the opposite direction. This construction has been devised to prevent deterioration of the strength of the boundary between the first and second semicircumference regions. Two semicircumference-long prepregs whose reinforcing fibers incline in opposite directions with respect to the axis of the shaft 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 a molding core material (mandrel) to manufacture the golf club shaft in a shorter period of time and reduce the degree of variation in the characteristics of products.
In the proposal disclosed in Japanese Patent Application No. HEI9-242340, 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
Onuki Masahide
Sumitomo Norio
Sumitomo Rubber Industries Ltd.
Wong Steven
LandOfFree
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