Adhesive bonding and miscellaneous chemical manufacture – Methods – Surface bonding and/or assembly therefor
Reexamination Certificate
1999-12-28
2004-07-27
Aftergut, Jeff H. (Department: 1733)
Adhesive bonding and miscellaneous chemical manufacture
Methods
Surface bonding and/or assembly therefor
C156S188000, C428S035700, C428S036100, C473S316000, C473S319000
Reexamination Certificate
active
06767422
ABSTRACT:
The present invention relates to a shaft for golf clubs (hereinafter referred to simply as shaft). More specifically, the present invention relates to a shaft that is 35-50 percent lighter than conventional shafts while providing the same outer diameter and the same characteristics as conventional shafts such as flexural rigidity, flexural strength, torsional rigidity, torsional strength, and crushing strength.
In one type of golf club, a fiber-reinforced composite material (hereinafter referred to as FRP) is used in forming the shaft. In this type of shaft, a fiber-reinforced fiber material is formed by lining up reinforcing fibers in a “one-directional” pre-impregnation (hereinafter referred to as prepregs) and then immersing the aligned fiber material in a resin. The shaft is then formed by wrapping the fiber-reinforced material around a tapered metal mandrel and hardening the composite in a laminated state. This type of golf club shaft is widely used due to its high specific rigidity, specific strength, and the degree of freedom allowed in its design.
FRP shafts often use a two-layer structure to form the reinforced composite. An inner layer is formed of angled fibers (angled layer) and an outer layer is formed from straight fibers (straight layer). In the angled layer, prepregs are glued together so that the reinforcing fibers form angles of +theta; −theta relative to the longitudinal axis of the shaft. In the straight layer, the prepregs are stacked so that the reinforcing fibers are within a +/−20 degree range relative to the longitudinal axis of the shaft.
In recent years, there has been a trend toward creating lighter golf club shafts. By lightening the shaft it is possible to produce a larger “sweet spot” in the golf club head. With a larger “sweet spot” in the golf club head, golf clubs can be designed to accompany higher head speeds, longer shafts, and larger heads.
Conventionally, lighter golf club shafts are designed and manufactured by simply reducing the number of straight layers and angled layers that make up the shaft. As a consequence of reducing the number of layers there is a reduction in flexural rigidity, flexural strength, torsional rigidity, torsional strength, and crushing strength. These reductions in strength and rigidity are undesirable.
Alternative methods have been attempted to create lighter shafts which minimize the adverse effects on strength and rigidity. Two methods which provide for a lighter shaft while maintaining flexural rigidity and torsional rigidity are as follows:
(1) reduce the number of straight layers and/or angled layers while also using a reinforcing fiber that has a high elasticity in these layers; and
(2) reduce the thickness of the layers by changing the shape of the shaft itself, primarily by increasing the outer diameter.
In method (1), the flexural rigidity and torsional rigidity are comparable with conventional shafts. However, reinforcing fibers with high elasticity generally have low strength. Golf club shafts designed according to method (1) result in flexural and torsional strengths which are the same as, or even lower than, golf clubs shafts which simply have the number of layers reduced.
In method (2), increasing the outer diameter near the grip is effective in maintaining flexural rigidity. However, the increased grip diameter results in a golf club shaft that is difficult to handle, making the arrangement impractical.
Japanese laid-open utility model publication number 62-33872 discloses a method for improving the torsional rigidity and torsional strength in FRP shafts. According to this method, an FRP shaft includes angled layers and straight layers which are formed with the angled layer as the outermost layer. However, the finishing process of the FRP shaft, i.e., polishing and the like, can result in a loss in the angled layer. The thickness of the angled layer is needed to maintain torsional rigidity and torsional strength. Thus, FRP shafts made according to this method do not have consistent quality. In addition, this method does not provide for a lighter FRP shaft.
Japanese laid-open patent publication number 8-131588 provides for another method of improving an FRP shaft. According to this method, an FRP shaft includes (starting from the inner most layer): a thin hoop layer, a straight layer, and an angled layer. As in the method previously described above, the finishing process of the FRP shaft, i.e., polishing and the like, can result in the loss of the angled layer needed to maintain torsional rigidity and torsional strength. Thus, FRP shafts made according to this method do not have consistent quality and do not result in a lighter FRP shaft.
OBJECTS AND SUMMARY OF THE INVENTION
It is an object of the present invention to provide a golf club shaft which overcomes the drawbacks in the prior art.
It is another object of the present invention to provide a lighter golf club shaft that overcomes the drawbacks of the prior art.
It is yet another object of the present invention to overcome the problems of the prior art and to provide a shaft that is 35-50% lighter than a conventional shaft.
It is a further object of the present invention to overcome the problems of the prior art and to provide a shaft that is 35-50% lighter than a conventional shaft while maintaining the same outer diameter as a conventional shaft.
It is another object of the present invention to overcome the problems of the prior art and to provide a shaft that is 35-50% lighter than a conventional shaft while maintaining the flexural rigidity, flexural strength, torsional rigidity, and torsional strength of a conventional shaft.
It is yet another object of the present invention to overcome the problems of the prior art and to provide a shaft that is 35-50% lighter than a conventional shaft while maintaining the outer diameter, flexural rigidity, flexural strength, torsional rigidity, and torsional strength of a conventional shaft.
It is another object of the present invention to provide a light-weight golf club shaft that is formed by laminating a plurality of fiber-reinforced composite materials. The laminate is made by forming the following layers in sequence starting with the inner most layer: a first angled layer; a first straight layer; a second angled layer; and a second straight layer. Each layer is a fiber-reinforced composite material. The laminated layers extend over the entire length of the shaft.
It is another object of the present invention to provide a light-weight golf club shaft formed by laminating a plurality of fiber-reinforced composite materials, the laminate being made by forming a first angled layer, a first straight layer formed on the first angled layer; a second angled layer formed on the first straight layer, and a second straight layer formed on the second angled layer. Each layer is a fiber-reinforced composite material. The laminated layers extend over the entire length of the shaft. The second angled layer has a thickness of 0.04-0.10 mm, and reinforcing fibers contained therein have an orientation of 35-75 degrees relative to the longitudinal direction of the shaft. The shaft has a torsional strength of at least 120 kgf×m×degrees (1200 N×m×degrees) and a weight of 30-40 g.
Briefly stated, the present invention provides a golf club shaft that is 35-50 percent lighter than a conventional shaft while maintaining the outer diameter and structural characteristics of conventional shafts. The shaft has at least four layers of fiber reinforced material. The fiber reinforced layers are from innermost to outermost: a first angled layer; a first straight layer; a second angled layer, and a second straight layer. The angled layers are formed by bonding together two materials, each with fibers aligned in different directions. The second angled layer maintains the proper strength and rigidity of the shaft while keeping the shaft as light weight as possible. Aligning the second layer's fibers at an angle of 35-75 degrees with respect to the longitudinal direction of the sha
Anai Katsumi
Atsumi Tetsuya
Ibuki Tsutomu
Takiguchi Ikuo
Aftergut Jeff H.
Darby & Darby
Fischer Justin
Mitsubishi Rayon Co. Ltd.
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