Games using tangible projectile – Golf – Club or club support
Reexamination Certificate
2002-04-30
2004-12-28
Blau, Stephen (Department: 3711)
Games using tangible projectile
Golf
Club or club support
C473S349000
Reexamination Certificate
active
06835143
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method of evaluating a golf club, and to a golf club which has been evaluated in accordance with the method of evaluating a golf club. In particular, the present invention relates to a method of evaluating a golf club, and a golf club, in which the size of a sweet area of the golf club is able to be accurately indicated, and to a golf club set having a plurality of such golf clubs in which the golf clubs differ in loft angle and in club length.
2. Description of the Related Art
Golfers often rely upon the golf clubs in order to obtain a good score, in addition to improving their skill in order to achieve good golf play. A good performance of the golf clubs is therefore always desired by many golfers. The good performance, for example, has a meaning of long distance of a golf ball flight and ease of hitting a golf ball. In particular, the ease of hitting is evaluated from a subjective standpoint along with an objective standpoint in which the variation of the golf ball flight becomes small between cases of hitting a golf ball at the center of the golf club face and cases of hitting a golf ball off the center. This is generally discussed by the size of the sweet area. Namely, golf clubs are evaluated such that the larger the sweet area of the golf club, the smaller the variation (drop in flight distance, and lateral shift of a golf ball flight) becomes between cases of hitting at the center and cases of hitting off the center.
The size of the sweet area of the golf club depends upon the golf club head, and as stated later, is mainly evaluated in accordance with the numerical value of a moment of inertia about a specific axis of the golf club head itself. In other words, from the numerical value of the moment of inertia, the degree of a steady performance of the golf club head when the golf club head hits a golf ball off a sweet spot can be obtained, and the larger the numerical value of the moment of inertia, the less unsteady performance the golf club head has in hitting off the center, and the more similar the golf ball flight of hitting off the center comes to a golf ball flight of hitting at a sweet area. Namely, when the difference between cases of hits at the center of the golf club and cases of hits off the center becomes small, it can be evaluated that the golf club has a large sweet area.
In Japanese Patent No. 2851542, a technique is disclosed for increasing the moment of inertia with respect to a golf club head, in a state in which its sole is placed in a horizontal plane, about a horizontal axis parallel to the plane of the club face through the center of mass (moment of inertia about an X axis in the above patent), and the moment of inertia about a vertical axis through the center of mass (moment of inertia about a Y axis in the above patent) , thereby enlarging the sweet area, by setting the thickness and the volume of the golf club head.
In particular, the most generally used value of the moment of inertia by those skilled in the art is a value of the moment of inertia about the vertical axis parallel to the vertical direction through the center of mass of the golf club head, also shown in the above Japanese Patent No. 2851542. The value of the moment of inertia measured around this axis is generally used for evaluating the size of the sweet area.
The above axes about which the moments are measured are selected on the assumption that the golf club head rotates in directions when the sweet area of the golf club head is missed. For example, the axis parallel to the plane of the hitting surface of the golf club head, through the center of mass, and in a horizontal direction shown in Japanese Patent No. 2851542 (the X axis shown in
FIG. 1
of the above patent) is an axis of rotation of the golf club head when a golf ball is hit while missing the sweet area up and down in a vertical direction. The axis in a vertical direction through the center of mass of the golf club head (the Y axis shown in
FIG. 1
of the above patent) is an axis of rotation of the golf club head when a golf ball is hit while missing the sweet area of a golf club head in a toe and heel (lateral) direction.
When an ordinary golfer misses the sweet area while hitting there is no certain tendency of the miss, in the toe and heal direction or in the vertical direction, and generally hitting points on the golf club surface are variously varied around the sweet area.
However, the moment of inertia about the axis parallel to the plane of the hitting surface of the golf club head, through the center of mass, and in a horizontal direction, such as that of the above Japanese Patent No. 2851542, can only indicate the steady performance of the golf club head when hitting while missing the sweet area in a vertical direction, namely the size of the sweet area in the vertical direction. Further, the moment of inertia around the axis in a vertical direction through the center of mass can only indicate the steady performance of the golf club head when hitting while missing the sweet area in a toe and heel direction, namely the size of the sweet area in the toe and heel direction.
The two moments of inertia of the above Japanese Patent No. 2851542 therefore cannot be used as indicators for unambiguously and accurately evaluating the size of the sweet area based upon a golfer's tendency that the hitting points are variously varied around the sweet area.
In other words, although the golf club head can be made to have relatively steady performance even in cases in which an ordinary golfer hits while missing the sweet area, and a golf ball flight relatively similar to a golf ball flight that occurs when hitting the ball at the sweet area can be stably realized, by evenly increasing the moment of inertia about the axis around the toe and heel direction, and the moment of inertia about the axis of the up and down direction, it is difficult to accurately increase the size of the sweet area quantitatively by increasing these moments of inertia, and it is difficult to accurately indicate the size of the sweet area by these moments of inertia.
Additionally, golfers have different skill levels such as those of beginners, intermediate golfers, and further advanced golfers. For example, beginners who often hit a golf ball while missing the sweet area, wants to select a golf club which will make almost the same golf ball flight as that of hitting at the sweet area, even when the sweet area is missed, and which impresses beginners a good sense of stability. On the other hand, there are many times when an advanced golfer will intentionally hit the golf ball off the sweet area in order to control the flight of the golf ball by subtly changing the striking direction of the ball and imparting spin to the ball. Advanced golfers desire to select a golf club with good controllability in which the ball flight can be controlled by the extent that a golf ball is hitted off the sweet area intentionally.
Although there are golf clubs classified toward advanced golfers, intermediate golfers, and beginning golfers in accordance with their level of skill, the golfer must evaluate a golf club subjectively by hitting it numerous times in order to select a golf club having a suitable size of the sweet area for that golfer. However, the evaluation cannot be obtained only from the size of the golf club sweet area, but from factors such as the moment of inertia around the axis of the golf club shaft, and the set value of the lie angle of the golf club head and the like, as the overall performance.
Therefore, whether a golf club is one impressing golfers sense of stability and producing results almost the same as those of hitting at the sweet area even when the sweet area is missed, whether it is one impressing golfers good controllability in which the ball flight can be controlled by the extent at which the sweet area is missed, or whether the golf club is one located between these characteristics, discerning the stability and controllability of golf clubs
Blau Stephen
Finnegan and Henderson, Farabow, Garrett & Dunner, L.L.P.
The Yokohama Rubber Co. Ltd.
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