Games using tangible projectile – Golf – Club or club support
Reexamination Certificate
1998-11-25
2004-03-16
Blau, Stephen (Department: 3711)
Games using tangible projectile
Golf
Club or club support
Reexamination Certificate
active
06705954
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a shaft for golf clubs (hereinafter referred to simply as shaft). More specifically, the present invention provides a grip region of a golf club shaft with improved rigidity.
In golf clubs, lighter shafts are desirable to improve the head speed during the swing. In addition, improved flexural rigidity at the grip is also desired to improve the feel of impact when striking the ball.
Japanese laid-open utility model publication number 63-133261 and Japanese laid-open utility model publication number 4-44968 disclose fiber-reinforced resin shafts where the rigidity of the shaft is adjusted by providing a member made from fiber-reinforced resin disposed over a section of the shaft.
U.S. Pat. No. 3,614,101 discloses a golf club shaft having a sloped section that expands toward the grip end. The sloped section has a gradient of 28/1000, a length of 254 mm, and an outer diameter at the grip end of 20.57 mm. A semi-sloped section having a slope gradient of 10.79/1000 is disposed closer to the end than the sloped section.
Japanese laid-open patent publication number 9-299524 discloses a fiber-reinforced resin golf club shaft having a tapered section toward the grip, a smalldiameter section toward the head, and a tapered center section. The tapered section toward the grip has a gradient between 2/1000 and 10/1000, a length between 200 mm and 600 mm, and a maximum outer diameter between 18 mm and 37 mm.
The golf club shafts disclosed in Japanese utility-model publication number 63-133261 and Japanese laid-open patent publication number 4-44968 are expensive to make. Both publications teach to use separate members which causes the production process to be complex and also substantially increases the cost of production.
Japanese utility model examined publication number 2529041 discloses another fiber reinforced resin shaft. The rigidity of the shaft is adjusted by having a metal layer disposed on the grip section of the shaft. The use of the metal layer also increases the complexity of the production process and substantially increases costs. Furthermore, since fiber-reinforced resin and metal do not have high adhesiveness, the grip section of the shaft is expected to lack durability.
With the shaft disclosed in U.S. Pat. No. 3,614,101, a straight shaft section approximately 150 mm in length is disposed between a sloped shaft section and a semi-sloped shaft section. At each point along the shaft where the sloped section meets the straight section there is a large change in the flexural rigidity of the golf club shaft. Since the straight section abuts two different sloped portions, the shaft has two locations where there is a large change in the flexural rigidity. When a golfer attempts to swing a club designed according to this method, the club shaft has variations in flexure. The flexure depends on a variety of factors including swing speed, cadence, ability and technique of the golfer's swing. The variations in the flexure of the shaft makes the golf club awkward to use.
Also, in the golf club shaft from Japanese laid-open patent publication number 9-299524 described above, there is a long section toward the end that has a uniform diameter. This section has less flexural rigidity and the kick point is too high. This results in a golf club shaft that is difficult to use.
OBJECTS AND SUMMARY OF THE INVENTION
It is an object of the present invention to provide a golf club shaft which overcomes the drawbacks of the prior art.
It is another object of the present invention to provide an improved grip section in a golf club shaft that overcomes the drawbacks of the prior art.
It is yet another object of the present invention is to provide a golf club shaft and method for producing the same where the rigidity is appropriately high, a kick point is formed at an appropriate position, the shaft is easy to use, and production can be performed inexpensively and easily.
It is an object of the present invention to provide a golf club shaft with a reduced number of parts.
It is another object of the present invention to provide a light weight golf club shaft which has an appropriate hardness and rigidity in the grip section.
It is yet another object of the present invention to provide a light weight golf club shaft with an appropriate hardness and rigidity in the grip section that provides a comfortable feel when hitting a golf ball.
It another object of the present invention to provide a light weight golf club shaft with an appropriate hardness and rigidity in the grip section that minimizes unnecessary wrist movements when hitting a golf ball.
It another object of the present invention to provide a light weight golf club shaft with an appropriate hardness and rigidity in the grip section that provides an appropriate kick point in the shaft.
It another object of the present invention to provide a light weight golf club shaft with an appropriate hardness and rigidity in the grip section that provides a good strength distribution along the shaft.
It is an object of the present invention to form a golf club shaft with a sloped section having a specific slope gradient where production is simplified by reducing the number of required parts. The shaft is light and has appropriate hardness, provides good rigidity at the grip section of the shaft, has good strength distribution along the shaft, and provides an appropriate kick point position along the shaft. The improvements provide a golf club with a good feel when hitting balls. The shaft has a large outer diameter at the grip section which restricts unnecessary movements at the wrists during golf club swinging and thereby improving the aim of the ball.
It is an object of the present invention to provide a golf club shaft having a sloped section with a length of 200-350 mm and a grip end with an outer diameter of 18-25 mm.
It is a further object of the present invention to provide a golf club shaft with a sloped section having a length of 200-350 mm and a grip end with an outer diameter of 18-25 mm which results in improved performance.
It is yet a further object of the present invention to increase the rigidity in the golf club shaft by forming a semi-sloped section at a position further toward the end than the sloped section with a slope gradient of 4/1000-13/1000.
It is yet another object of the present invention to provide a golf club shaft where a golf club head can be easily attached easily to the end of the shaft by forming a uniform-diameter section with a length of 40-125 mm at the end of the shaft.
Briefly stated, the present invention provides for a golf club shaft having an optimal set of materials and sloped sections provides appropriately high rigidity, ease of use, and is inexpensive and easy to manufacture. A sloped section expands toward a grip end of the shaft. The sloped section has a slope gradient from 15/1000 to 35/1000 and a length from 200 to 350 mm. The outer diameter of the grip end is from 18 to 25 mm. On the side of the sloped section toward an end, there is formed a semi-sloped section with a slope gradient from 4/1000 to 13/1000. A kick point is formed at a position from 40% to 46% from the small-diameter end relative to the total shaft length. The number of required parts is small while production is simple. The shaft is light, has appropriate hardness, and. high rigidity at the grip. Furthermore, the strength of the shaft is balanced and provides a good feel when hitting a ball. Production of the golf club shaft can be accomplished with standard materials such as fiber-reinforced resins. By wrapping a fiber-reinforced resin around a mandrel and rolling the material on a base which is heated to an optimal temperature, the strength and rigidity of the shaft can be optimized. Multiple layers can be overlaid to provide any desired strength and rigidity required. The rolled shaft is then heated to set the resin and produce a golf club shaft of optimal performance and reduced cost.
According to an embodiment of the present invention, there is provided for a golf clu
Atsumi Tetsuya
Ibuki Tsutomu
Takiguchi Ikuo
Blau Stephen
Mitsubishi Rayon Co. Ltd.
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