Golf club shaft

Details Golf club shaft Golf club shaft

1999-02-18

2001-04-10

Chapman, Jeanette (Department: 3711)

Games using tangible projectile

Golf

Practice swingable implement or indicator associated with...

C473S409000, C073S847000, C073S849000

Reexamination Certificate

active

06213888

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a golf club shaft, and in particular to a golf club shaft which adapts to the characteristics (type) of a golfer's swing.
2. Description of the Related Art
When selecting golf clubs to suit each golfer, the conventional method has been to do so by feel as a result of actually swinging several different clubs, but the question remains that it is not clear if the judgement is a correct one or not.
Meanwhile, it is normal to choose a fairly pliable golf club shaft for a beginner or for a woman, and a relatively hard one for a professional or a golfer with a powerful stroke. There is an element of preference, and it is often impossible to generalize, but again the disadvantage is that the selection has had to be based on feel.
What is more, there is also a problem in that there has been no objective means of grasping the characteristics of each golfer's swing as such for the purpose of practicing, correcting or improving swing technique, and it has been necessary to rely on subjective or empirical criteria.
It is true that there are methods of detecting the bending strain (stress) which accompanies a swing by attaching a strain gauge to the grip section of the golf club, thus monitoring the degree of force which comes into play as the result of a swing. However, this method of detection consists simply of attaching a single strain gauge, which not only makes it difficult to grasp a golf swing objectively, but also extremely difficult to select a golf club or golf club shaft to suit each golfer.
In view of the foregoing problems, it is an object of the present invention, having analyzed golf swings objectively, to provide a golf club shaft can be selected in accordance with the swing of each golfer.
It is a further object of the present invention to classify golfers' swings into four types, and to provide a golf club shaft which allows the club most suited to each golfer to be prepared.
It is yet a further object of the present invention to provide a golf club shaft which permits quantizing the differences between the four types of club, so as to allow the club most suited to each golfer to be prepared.
SUMMARY OF THE INVENTION
The inventors of the present invention have noticed that irrespective of whether they are beginners, intermediates or professionals, or which sex they belong to, golfers' swings can be classified into four types (I type, P type, D type and J type), and that these four types can be classified according to specific physical quantities, namely torque and kick point as measured with the aid of the third strain gauge. Accordingly, the present invention is a golf club shaft wherein are provided a first strain gauge attached to a first side of the shaft facing the striking direction, a second strain gauge attached to a second side of the shaft facing the address direction at right-angles to the striking direction, and a third strain gauge which is capable of measuring the twist of the shaft, detection signals from these gauges being used to classify the shaft into four types according to the swing type of each golfer, these four types of shaft being specified in accordance at least with either torque or kick point.
The abovementioned four shafts may be termed the I-type shaft, P-type shaft, D-type shaft and J-type shaft.
The abovementioned torque can be reduced gradually in order from the I-type shaft through the P-type shaft and the D-type shaft to the J-type shaft.
The abovementioned kick point can be increased gradually in order from the I-type shaft through the P-type shaft and the D-type shaft to the J-type shaft.
The abovementioned torque can be set in the case of the I-type shaft at between 5.6° and 7.2°, preferably 5.8°, in the case of the P-type shaft at between 4.6° and 5.0°, preferably 4.8°, in the case of the D-type shaft at between 4.0° and 4.4°, preferably 4.2°, and in the case of the J-type shaft at between 3.4° and 3.8°, preferably 3.6°.
The abovementioned kick point can be set in the case of the I-type shaft at between 38% and 42%, preferably 40%, in the case of the P-type shaft at between 40% and 43%, preferably 41.5%, in the case of the D-type shaft at between 42% and 45%, preferably 43%, and in the case of the J-type shaft at between 44% and 47%, preferably 44.5%.
It is possible to ensure that if Ti (where i=the I-type shaft, the P-type shaft, the D-type shaft and the J-type shaft) represents the torque, M represents a value in the striking direction or in the direction at right-angles to the striking direction, whichever is the greater, based on the detection signals from the first and second strain gauges, c is a constant, and di is a constant for each type, the formula Ti=1/(c·M+di) obtains.
It is possible to ensure that if KPi (where i=the I-type shaft, the P-type shaft, the D-type shaft and the J-type shaft) represents the kick point, Ti represents the torque for each type, and e, f and g are constants, the formula KPi=e·Ti
2
+f·Ti+g obtains.
It is possible for the abovementioned shaft to be manufactured from carbon fiber reinforced plastics or glass fiber reinforced plastics.
It should be added that the classification of the abovementioned golf club shafts into four types has proven that, contrary to conventional belief or conjecture, there is no connection with the flex of the shaft.
In other words, the characteristics of each golfer's swing type can be depicted graphically by representing the degree of strain (strain stress) in the horizontal direction (striking direction, H axis) and that in the vertical direction (direction at right-angles to the striking direction, V axis) during the action of swing as rectangular coordinates (H-V diagram). By analyzing the degree of twist and swing time in addition to the abovementioned strain stress, it is aimed to render the swings of individual golfers into patterns, and to provide a type of golf shaft suited to each of these patterns.
The golf club shaft to which the present invention pertains is classified by torque and kick point values in accordance with patterns measured and analysed from golfers' swings. Once the swing type of each golfer is classified, it is possible immediately to recommend or select a shaft suited to that golfer's swing.
In particular, the fact that four types are specified on the basis of torque and kick point makes it possible to select objectively and swiftly a shaft which is suited to each golfer and easy to swing, rather than relying on feel as hitherto.


REFERENCES:
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patent: 3792863 (1974-02-01), Evans
patent: 3806131 (1974-04-01), Evans
patent: 3945646 (1976-03-01), Hammond
patent: 4157181 (1979-06-01), Cecka
patent: 5792000 (1998-08-01), Weber
patent: 5821417 (1998-10-01), Naruo
patent: 5947839 (1999-09-01), Kusumoto
patent: 10244023 (1998-09-01), None
M. Watari, et al., “Studies on Golf Swing Type and Matching Golf Club to the Player”, presented at the World Scientific Congress of Golf, University of St. Andrews, Scotland, Jul. 20-24, 1998, 1 page.
Nippon Shaft, “Studies on Golf Swing Type and Matching Golf Club to the Player”, presented at the World Scientific Congress of Golf, University of St. Andrews, Scotland, Jul. 20-24, 1998, pp. 2-10.

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