Patent Application
20130143689
1. Field of the Invention
The present invention relates to a golf club shaft, and more specifically, to a golf club shaft made of fiber-reinforced resin. Further, the present invention relates to a golf club having the golf club shaft.
2. Description of the Related Art
Golf club shafts may be classified into what are called a steel shafts and carbon shafts. The carbon shaft is widely used in view of lightness, the high degree of design freedom and the like.
The carbon shaft is made of fiber-reinforced resin in which a carbon fiber is used as a main fiber. As a method of manufacturing the carbon shaft, a sheet winding method is known (see JP-A-2010-259694). In this manufacturing method, a prepreg sheet is wound on a mandrel (core bar) and a wrapping tape is further wound thereon. Then the prepreg is heated to be cured, thereby making the carbon shaft.
Since a golf club has large kinetic energy as a head end on which a head is fixed is heavy, it is possible to give a large initial velocity to a ball at the time of swing, thereby making it possible to increase a carry of the ball. However, if only the head end is heavy, the center of gravity of the club is excessively inclined to the head end, and thus, the swing becomes hard. For this reason, when the head end of the shaft is made heavy, a grip end of a base is also made heavy. Further, if the head end and the grip end are heavy in this way and an intermediate portion is light, a follow-through at the time of swing is enhanced. In this way, in the golf club, since the carry of the ball and the swing performance are changed according to the weight distribution on the head end and the grip end, the weight adjustment on both the sides has been performed at the time of golf club design in the related art.
Since the weight adjustment becomes different according to physical strengths or preferences of players, it is necessary to prepare various heads and shafts. However, to prepare the various heads and shafts having different weights causes an increase in manufacturing cost and storage cost. Thus, the weight adjustment has been performed by a simple method in which a plurality of types of heads and shafts having different weights are made, and then, a lead plate is attached to the head in a case where the head end is heavy and a lead plate is attached to the inside of the grip of the shaft in a case where the grip end is heavy.
If the weight on the grip end of the carbon shaft is made heavy due to the lead plate attachment, the weight of the shaft is lighter than that of a metal shaft made of a metallic tube in the related art. Further, since the lead plate having a large specific gravity can be only locally attached, it is difficult to increase the weight of the entire grip end, and thus, the rotational moment is changed according to the grip position of a player.
An object of the invention is to provide a golf club shaft in which the weight on the striking face is increased by distributing, on the striking face, a large amount of prepregs where carbon fibers are distributed, and a golf club that uses the golf club shaft.
According to an aspect of the invention, there is provided a golf club shaft including a prepreg containing a carbon fiber, wherein the prepreg is winded and cured, and a winding thickness of the prepreg on a striking face is larger than a winding thickness of the prepreg on any other portion. By increasing the weight of the striking face in this way, it is possible to dispose the center of gravity on the striking face and to achieve a golf club having a small moment for easy swing. Further, even though the weight of the head is increased, it is possible to achieve a golf club having a balance that is not different from that of a golf club in the related art.
By increasing the winding thickness of the prepregs on the head end compared with the winding thickness of the prepregs in the intermediate portion, it is preferably possible to increase the strength on the head end;
The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawing which is given by way of illustration only, and thus is not limitative of the present invention and wherein:
Hereinafter, embodiments of the invention will be described with reference to the accompanying drawings.
In the manufacturing method, the mandrel 10 and prepregs 11 to 21 are used. A central axis line of the mandrel 10 is a straight line. The shape of a cross section perpendicular to the central axis line of the mandrel 10 is circular. As shown in
Preferably, after a parting agent is coated on the surface of the mandrel 10, the prepregs 11 to 21 of a sheet shape are sequentially wound. The prepregs 11 to 21 include a carbon resin and a matrix resin.
In the present embodiment, in the prepregs 11, 14, 16, 18, 19, 20 and 21, fibers are orientated in a straight direction, that is, in a shaft length direction. In the prepregs 15 and 17, fibers are oriented in a hoop direction, that is, in a shaft circumferential direction. Here, the fibers of the prepreg 19 may be in the hoop direction. In the prepreg 12, the fibers are oriented in a biased direction of +45° (direction oblique to the shaft length direction), and in the prepreg 13, the fibers are oriented in a biased direction of −45°. Here, the fibers of the prepreg 12 may be oriented by the angle of −45°, and the fibers of the prepreg 13 may be oriented by the angle of +45°. Further, the biased direction is not limited to 45°, and may have the range of 30° to 60°.
The prepregs 11 and 14 to 21 have a width to be wound on the outer circumference of the mandrel 10 by one round. The prepregs 12 and 13 have a width to be wound on the outer circumference of the mandrel 10 by a plurality of rounds, for example, 2 to 5 rounds.
The prepregs 12, 13, and 15 to 19 have a length extending over the entire length of the shaft. The prepregs 11, 20 and 21 have a length of 8% to 20% of the entire length of the shaft, and particularly, a length of about 10 to about 15% thereof to be distributed only on the head end of the shaft. By winding the prepregs 11, 20 and 21, the winding thickness of the head end is increased. The prepreg 21 has a triangular shape in which the width becomes large as it goes to the head end, and thus, the vicinity of the head end of the shaft has a cylindrical shape of an approximately uniform diameter. The vicinity of the head end is inserted into a hosel hole of a head.
The prepreg 14 is distributed only on the striking face, and the length thereof in the shaft length direction is preferably 15% to 45% of the entire length of the shaft, particularly, 20% to 40%, and more particularly 25% to 35%. By selecting the number of the prepregs 14, the winding thickness of the striking face is increased, as shown in
It is preferable that the thicknesses of the prepregs 12 and 13 be 0.125 mm or less, and particularly, about 0.05 mm to about 0.1 mm. It is preferable that the thicknesses of the prepregs 15 and 17 be 0.1 mm or less, and particularly, about 0.02 mm to about 0.05 mm. It is preferable that the thicknesses of the prepregs 16, 18 and 19 be 0.125 mm or less, and particularly, about 0.05 mm to about 0.1 mm. It is preferable that the thicknesses of the prepreg 14 be 0.05 mm to 2.0 mm, and particularly, about 0.075 mm to about 0.15 mm. It is preferable that the thicknesses of the prepregs 11, 20 and 21 be 0.05 mm to 0.2 mm, and particularly, about 0.075 mm to about 0.15 mm.
It is preferable that the volume fraction of fibers in the respective prepregs 11 to 21 be 60 vol % to 80 vol %, and particularly, about 70 vol % to about 75 vol %. It is preferable to use an epoxy resin or the like as the resin.
It is preferable that the tensile elasticity of the carbon fibers in the prepregs be 10 ton/mm2 to 46 ton/mm2 in the case of the straight direction, and particularly, about 20 ton/mm2 to about 40 ton/mm2. Further, it is preferable that the tensile elasticity thereof be 8 ton/mm2 to 30 ton/mm2 (about 78.4 GPa to about 294 GPa) in the case of the hoop direction, and particularly, about 10 ton/mm2 to about 24 ton/mm2. It is preferable that the carbon fibers oriented in the biased direction have a high modulus elasticity of 40 ton/mm2 (about 392 GPa) or more, for example, 40 ton/mm2 to 55 ton/mm2.
In a case where the prepregs 11 to 21 are wound on the mandrel 10, the prepregs 11 to 21 may be wound one by one, or may be wound while pasting a part of the prepregs. For example, the prepregs 15 and 16 may be pasted together, or the prepregs 17 and 18 may be pasted together. An operation of winding the prepregs 11 to 21 on the mandrel 10 may be manually performed, or may be performed by a winding machine (also referred to as a rolling machine). After the prepregs 11 to 21 are wound on the mandrel, a wrapping tape winding process is performed. Although not shown, the wrapping tape is wound in a spiral shape.
After the winding process, a curing process is performed by heating, and thus, the matrix resin in the prepregs is cured.
After the curing process, extraction of the mandrel and removal of the wrapping tape are performed, to thereby obtain a cured tubular body (element tube). The opposite ends of the element tube are cut as necessary and are ground, to thereby obtain a golf club shaft 3 (see
In the shaft 3, it is preferable that the thickness of the rearmost end of a striking face 3c be 2.5 mm to 1.0 mm, and particularly, 0.6 mm to 0.8 mm. It is preferable that the thickness of the head end of a head end 3a is 1.3 mm to 1.8 mm, and particularly, 1.4 mm to 1.7 mm. Further, it is preferable that the average thickness of an intermediate portion 3b is 0.4 mm to 0.7 mm, and particularly, about 0.5 mm to about 0.65 mm. It is preferable that the thickness of the rearmost end of the striking face 3c be larger than the average thickness of the intermediate portion 3b by 0.1 mm to 0.4 mm, and particularly, by 0.125 mm to 0.3 mm. By increasing the thickness of the striking face 3c in this way, the weight of the shaft 3 on the striking face is increased. It is preferable that a range L of the striking face 3c having a large thickness be 15% to 45%, particularly, 20% to 40%, and more particularly, 25% to 35% of the entire length of the shaft 3 from the striking face of the shaft 3.
In the case of a shaft for a wood golf club, the entire length of the shaft is about 1050 mm to about 1220 mm. In the case of the wood golf club shaft, it is preferable that the position of the center of gravity be present in the range of 52% to 57% from the head end of the shaft 3 on the head end. It is preferable that the weight of the shaft be about 40 g to about 50 g. Further, in this case, the outer diameter of a region that ranges from the head end to 250 mm be 8.9 mm to 9.5 mm. It is preferable that a portion between the head end 3a and the intermediate portion 3b and a boundary portion between the intermediate portion 3b and the striking face 3c have a taper of about 6.5/1000 to about 7.2/1000.
In this embodiment, since the thickness of the head end 3a is larger than that of the intermediate portion 3b, the strength of the head end 3a is high.
The layering example of the prepregs in
In the above description, only the carbon fibers are included in the prepregs, but other fibers such as glass fibers, silicon carbide fibers, alumina fibers, aromatic polyamide fibers or boron fibers may be mixed therein.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2011-264844 | Dec 2011 | JP | national |
