Games using tangible projectile – Golf – Club or club support
Reexamination Certificate
2002-08-21
2004-07-20
Blau, Stephen (Department: 3711)
Games using tangible projectile
Golf
Club or club support
C473S318000
Reexamination Certificate
active
06764414
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a golf club shaft and more particularly to a lightweight golf club shaft, made of a fiber reinforced resin, which has an improved vibration-damping performance and gives a good feeling to a player when the player hits a golf ball with a golf club composed of the golf club shaft.
2. Description of the Related Art
In recent years, a golf club shaft composed of a reinforcing fiber such as a carbon fiber having a high specific strength and a high specific rigidity is manufactured and commercially available. As the specific strength and the specific rigidity of the carbon fiber become higher, the lightweight golf club shaft can be manufactured.
As the golf club shaft becomes more lightweight, the head speed of a golf club becomes increasingly higher when it is swung. Thus the player can hit a golf ball a longer distance with the golf club. On the other hand, as the golf club shaft becomes more lightweight, vibrations and impacts the player feels unpleasant are generated increasingly when the player hits the golf ball with the golf club. As the golf club shaft becomes more lightweight, the frequency of the vibration thereof becomes higher than the conventional golf club shaft. Therefore in recent years, players are increasingly damaged at their elbows and shoulders by vibrations and impacts generated when they hit the golf ball with golf clubs composed of the lightweight golf club shafts.
To suppress the vibrations generated when the player hits the golf ball, many proposals are made. For example, in Japanese Patent Application Laid-Open Nos. 9-216958 and 10-36638, resinous particles of an ethylene copolymer and rubber particles are mixed with the resin of the fiber reinforced resin layer to form the prepreg composed of the fiber reinforced resin superior in vibration suppression performance and resistance to impacts.
In the golf club shaft having the three-layer construction disclosed in Japanese Patent Application Laid-Open No. 5-123428, to obtain vibration absorption performance and a soft feeling, the vibration suppression material layer is inserted into the fiber reinforced resin layer. In the golf club shaft disclosed in Japanese Patent Application Laid-Open No. 10-71222, the vibration absorption member having a weight and the elastic material (foam) covering the weight is mounted on the grip part of the golf club shaft.
In the prepreg disclosed in Japanese Patent Application Laid-Open Nos. 9-216958 and 10-36638, the prepreg itself has vibration suppression performance. However, in the case where the prepreg is used to compose the golf club shaft, the prepreg is incapable of achieving dramatic vibration-damping performance to such an extent that the player can feel and further allowing the player to hit the golf ball a long distance with a golf club composed of the golf club shaft.
In the golf club shaft disclosed in Japanese Patent Application Laid-Open No. 5-123428, it is difficult to design the golf club shaft in such a way as to flex it. Since the degree of freedom in designing the golf club is low, it is difficult make it lightweight and increase the flight distance of the golf ball while allowing the golf club shaft to have vibration-damping performance. Further it is difficult to mold the material for the golf club shaft. Thus the golf club shaft has a problem that there is a large lot-to-lot variation in its vibration suppression function. In the golf club shaft disclosed in Japanese Patent Application Laid-Open No. 10-71222, since the metal having a high specific gravity is used as the weight, the golf club shaft is heavy and thus a player has difficulty in swinging it. In addition, it is complicated to make a design regarding the weight of the golf club shaft and form the vibration absorption member. The member in direct contact with the golf club shaft is fixed with parts harder than the elastic material. The construction of the golf club shaft has a limitation in making it lightweight and improving its vibration absorption performance.
SUMMARY OF THE INVENTION
The present invention has been made in view of the above-described problems. Therefore it is an object of the present invention to provide a golf club shaft which is more lightweight and hits a golf ball a longer distance than a conventional golf club shaft and relieves vibrations and impacts to be transmitted to a player to allow the player to feel it softer than the conventional golf club shaft.
To achieve the object, according to the present invention, there is provided a hollow pipe-shaped golf club shaft and composed of a laminate of prepregs. A vibration absorption member made of an elastic material whose tan &dgr; at 10° C. is not less than 0.7 is installed at least one portion inside the hollow pipe-shaped golf club shaft.
The vibration absorption member made of the tan &dgr; (loss tangent)-specified elastic material having high vibration-damping performance is installed inside the pipe-shaped golf club shaft. Thus although the golf club shaft is lightweight, a golf club composed of the golf club shaft is capable of hitting a golf ball a long distance, reducing vibrations and impacts generated when the golf ball is hit with the golf club, and giving a good feeling to a player. Since the vibration absorption member is inserted into a required position inside the hollow pipe of the golf club shaft and merely fixed thereto, it is easy to improve the vibration-damping performance of the golf club shaft.
An elastic material composing the vibration absorption member installed at least one portion inside the hollow pipe of the golf club shaft has the loss tangent (tan &dgr;) not less than 0.7 at 10° C. The larger the loss tangent (tan &dgr;) is, the larger the energy conversion of the vibration absorption member is. Therefore it is possible to suppress vibrations and impacts generated when the player hits the golf ball with the golf club. Thus it is possible to give an unpleasant feeling to a reduced extent when the player hits the golf ball with the golf club.
If the loss tangent (tan &dgr;) is less than 0.7, the vibration absorption member is incapable of displaying vibration/impact suppression effect sufficiently. From this point of view, the tan &dgr; is favorably not less than 1.0 and more favorably not less than 1.5. The upper limit of the tan &dgr; is not specified in the present invention, but for the reason of availability of a material, which can be used for the golf club shaft, the tan &dgr; is set to less than 5.0 and favorably to less than 4.0, and more favorably to less than 2.0.
It is preferable that the vibration absorption member has a body having a hollow portion, a central part connected to the body through a plurality of connection parts and disposed inside the hollow portion, a plurality of projected parts formed on a peripheral surface of the body and contacting an inner peripheral surface of the pipe-shaped golf club shaft.
It is preferable that the weight of the vibration absorption member is not less than 1 g nor more than 10 g; that the number of the connection parts is not less than two nor more than 10; and that the weight of the central part is not less than 10 wt % nor more than 60 wt % of a whole weight of the vibration absorption member. Owing to this construction of the vibration absorption member, its central part is capable of resonating with vibrations of the golf club shaft. Thus the vibration absorption member is capable of enhancing the vibration-damping effect to a higher extent.
The weight of the vibration absorption member is set to not less than 1 g nor more than 10 g and favorably to not less than 3 g nor more than 8 g.
If the weight of the vibration absorption member is less than 1 g, the vibration absorption member is incapable of displaying the vibration/impact damping effect sufficiently. On the other hand, if the weight of the vibration absorption member is more than 10 g, the entire golf club becomes heavy. Thus there is no degree of freedom in designing the weight of the
Blau Stephen
Sumitomo Rubber Industries Ltd.
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