Games using tangible projectile – Golf – Club or club support
Reexamination Certificate
1998-09-09
2001-02-27
Passaniti, Sebastiano (Department: 3711)
Games using tangible projectile
Golf
Club or club support
C473S342000, C473S345000, C473S346000, C473S349000, C473S350000
Reexamination Certificate
active
06193614
ABSTRACT:
BACKGROUND OF THE INVENTION
a) Field of the Invention
The present invention relates to a golf club, and more particularly to a golf club with an improved head.
b) Related Art
(1) A recent trend of the golf club is that the club head is made of a metallic material, and formed with a shell having a hollow interior. Increase of the club head size and thinning of the face portion of the club head and other tendency progress. The theory teaches that the size increase of the club head accrues to the increase of a moment of inertia and the enlargement of the sweet spot, and hence to the stabilization of the flying direction of a ball, and that the thinning of the club face accrues to reduction of the weight of the whole golf club, and hence to the increase of a flying distance. A specific example of the implementation of the theory is disclosed in Japanese Patent No. 2605926. In the example, the face portion of the golf club is 2 mm to 3.5 mm thick, the crown portion is 0.6 mm to 2 mm thick, and the sole portion is 1 mm to 3 mm thick. The face portion is broadened (40 mm or longer in vertical length and 70 mm or longer in horizontal length). The golf club thus dimensioned succeeds in stabilizing the ball flying direction and increasing the ball flying distance.
Thus, the thinning and enlarging of the face portion and the like improve the characteristics of the golf club indeed, but suffers from the following problems. Particularly the face portion (i.e. the ball striking surface) is liable to broken. A crack, formed in the ball striking surface, grows through its long time use. In other words, its durability is not satisfactory. For this reason, there is a limit in increasing the size of the club head, and hence reducing its weight and adjusting a weight distribution in the club head.
Proper selection of the material for the club head and the method of manufacturing the same may solve those problems to some extent. For example, where a &bgr; alloy is used for titanium, the face portion, for example, may be reduced in thickness since its strength is higher than that of a pure Ti &agr; alloy and &agr;&bgr; alloy. When the rolling is used for manufacturing the club head, the crystal grains are fined and increased in density, to increase a strength of the club head.
Use of those techniques still fails to achieve a satisfactory thinning and enlarging of the face portion. The reason for this will be described with reference to the related drawings attached to this specification.
Reference is made to
FIGS. 1
,
2
(
a
) and
2
(
b
) for explaining the whole golf club. Of those figures,
FIG. 1
is a view showing the whole construction of a golf club. FIG.
2
(
a
) is a front view showing a club head of the golf club, and FIG.
2
(
b
) is a cross sectional view taken on line A—A in FIG.
2
(
a
).
In those figures, reference numeral
1
is a shaft;
2
is a grip; and
5
is a club head. The club head
5
has a neck
6
to which the shaft
1
is attached, and its configuration is defined by a face portion (a ball striking surface)
7
, a top-side (crown) portion
8
, a toe-side portion
9
, a heel-side portion
10
, a sole portion
11
, and a back-face portion
12
. Those surface portions are demarcated by ridge lines
15
. Score line grooves
7
a
are formed in the face portion
7
to impart a spinning motion to a ball when striking the ball.
A deformation state of the club head when the face portion
7
of the club head strikes a ball will be described with reference to FIG.
3
. As shown in
FIG. 3
, as the result of the recent tendency of size increasing, the face portion
7
of the club head is configured to be short in height and long in width, and its depth (thickness) is h. In the area serving as a sweet spot of the face portion
7
, the horizontal length X is longer than the vertical length Y.
At the instant that the face portion
7
thus configured impacts against the ball, the face portion
7
is entirely deformed (deflected) toward the back-face portion. Specifically, an impact produced when striking the ball deforms the face portion
7
in the X and Y directions. In this case, an amount of deformation X
1
in the X direction is not equal to that Y
1
in the Y direction. The deformation amount Y
1
is larger than the deformation amount X
1
since the dimension of the face portion when viewed in the X direction is larger than that in the Y direction at the center P of the sweet spot when the deformation amounts are measured per unit length.
Thus, the deformation amount per unit length in the vertical direction is larger than that in the horizontal direction. Because of this, the face portion is liable to crack in the horizontal direction. With the increase of the head size, the horizontal size of the club head is larger, so that the deformation amount per unit length increases to further promote its fissuring.
The present invention was made in view of the facts that, when an impact is applied to the face portion, the deformation amount per unit length at the center on the face portion differs with the directions, viz., the deformation amount in the long-dimension direction of the face portion is different from that in the short-dimension direction, and that this hinders the thinning of the club head.
With the increase of the club head size, the face portion, for example, of the golf club is configured such that the horizontal length (the length in the long-dimension direction) is increased. Therefore, crack and breakage in the horizontal direction is liable to be formed in the face portion. In designing the conventional golf club, the above discovery is not taken into consideration, and a conventional measure taken for the crack formation problem is to merely increase the thickness of the face portion. The conventional technique is confronted with difficulties of reducing in thickness those surface portions and other surface portions of the club head for the reason that the thinning of those surfaces leads to formation of crack.
Accordingly, an object of the present invention is to provide a golf club with a club head which may be reduced in its thickness with no fear of impairing the durability and strength of the club head.
(2) As disclosed in Japanese Patent Laid-Open Publication No. Hei-6-269518), if the ball is greatly elastically deformed when it is hit, the energy imparted to the ball is consumed for the motion to restore the deformed ball to its original form. As a result, the flying distance of the ball is not increased.
To prevent the face portion of the club head from being deformed inward and permanently deformed so when hitting the ball, a ratio of a durability of &sgr; of the face portion to an elastic modulus (Young's modulus) E thereof (&sgr;/E) is set at 5×10
−3
or larger. In other words, when hitting the ball, the face portion is made elastically deformed inward, whereby an elastic deformation of the ball is minimized to thereby increase the flying distance of the ball.
Only increasing of a strength of the face portion to withstand some amount of deformation of the face portion fails to optimize a coefficient of rebound or restitution of the face portion when hitting the ball, to increase the flying distance, and to secure a directional stability of the ball. To prevent an extreme deformation of the ball when the face portion impacts on the ball and to optimize the coefficient of restitution of the face portion, it is necessary to adjust a flexure amount of the face portion. If a flexure amount of the face portion when hitting the ball is calculated in advance and the face portion is designed to have an optimum flexure amount when hitting the ball, it is possible to optimize the coefficient of restitution of the face portion, to increase the flying distance of the ball, and to secure the directional stability of the ball.
Through the investigation on the flexure characteristic of the face portion of the club head, the facts were discovered in that a flexure amount of the face portion per unit length when hitting the ball is larger in the vertical
Imai Yasuto
Kusumoto Harunobu
Matsuo Atsushi
Sasamoto Akinori
Daiwa Seiko Inc.
Liniak Berenato Longacre & White
Passaniti Sebastiano
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