Patent Application
20120295735
The present invention relates to a golf club shaft (carbon shaft) which is produced by winding and thermally curing prepregs (sheets) made of thermosetting resin and a golf club using this golf club shaft.
Prepregs are known as sheet materials made of toughened fibers (reinforced fibers, carbon fibers, etc.) impregnated with an uncured thermosetting resin. In the field of golf club shafts, a plurality of prepregs are wound on a mandrel that has the shape of a tapered shaft and are thermally cured into a tapered golf club shaft.
Patent Document 1: Japanese Unexamined Patent Publication No. H9-131422
Patent Document 2: Japanese Unexamined Patent Publication No. 2000-51413
In the golf club shaft 1 as described above, the fiber direction of the compressive rigidity holding layer 2 is limited to 90° and the fiber direction of the bending rigidity holding layer 4 is limited to 0°. Whereas, in the torsional rigidity holding layer 3, the more diversified the directions of the fibers included therein are, the higher the isotropy (torsional strength without regard to directions), which makes it possible to achieve a feeling close to the feeling one gets when hitting a golf ball with a steel shaft. This is a chief reason why a plain weave fabric prepreg, a triaxial woven fabric prepreg and a tetra-axial woven fabric prepreg are used for the torsional rigidity holding layer 3. Using the concept “degree (rate) of isotropy (frequency)” in regard to the magnitude of isotropy, the degree of isotropy is considered to increase in the order from a pair of bias layer prepregs, a plain weave fabric prepreg, a triaxial woven fabric prepreg to a tetra-axial woven fabric prepreg. Incidentally, the degree of isotropy of a steel shaft is the highest.
However, another problem is that there is a limit in thickness (weight) of the torsional rigidity holding layer 3. As long as there is a limit in the thickness, idea way for securing sufficient torsional rigidity with less number of plies (number of turns) of less number of prepregs needs to be devised. In other words, when the same or different types of prepregs having the same number of layers are used, a structure capable of further increasing the torsional rigidity is required.
The present invention has been devised in view of the above described problems, and an object of the present invention is to achieve a golf club shaft and a golf club using the same in which the isotropy of the prepregs configuring a torsion rigidity holding layer is high, and in which sufficient torsional rigidity can be secured with less number of plies of less number of prepregs.
If the structure of a conventional torsional rigidity layer in which, after a prepreg having a specific oblique fiber direction with respect to the longitudinal direction of a golf club shaft is wound, a prepreg whose fiber direction is different from the aforementioned oblique fiber direction is wound on the aforementioned prepreg, is revised, and if these prepregs whose fiber directions are mutually different are layered in advance and wound continuously by two turns or more with the prepregs remaining layered on each other, the degree of isotropy increases as the prepregs thus layered are regarded as a single prepreg; on the other hand, as the prepregs thus layered are each regarded as an independent prepreg, on both sides of this prepreg prepregs each having a different fiber direction lie over two turns or more; accordingly, the present invention has been achieved based on the findings that deviations between layers of each prepreg (deviations between fibers of each prepreg after it is thermally cured) can be reduced to consequently be capable of enhancing the torsional rigidity.
Namely, the golf club shaft according to the present invention is characterized by including a torsional rigidity holding layer made of a thermosetting resin which contains reinforced fibers extending obliquely to a longitudinal direction of the shaft, wherein the torsional rigidity holding layer comprises a multilayer set prepreg, in which at least two layers of prepregs made of reinforced fibers are impregnated with a thermosetting resin, wherein a plurality of prepregs in the multilayer set prepreg include reinforced fibers extending in mutually different directions; and wherein the multilayer set prepreg is continuously wound by at least two turns with the plurality of prepregs layered on each other.
In this specification, the term “reinforced fibers” denote not only carbon fibers but also various types of fibers such as alumina fibers, aramid fibers, Tyranno fibers, amorphous fibers, glass fibers, etc.
The multilayer set prepreg can be provided with a pair of multilayer set prepregs whose winding directions are mutually opposite.
It is desirable for the multilayer set prepreg to include a fabric prepreg which is made by impregnating fiber-reinforced fabric with a thermosetting resin, and a UD prepreg which is made by impregnating reinforced fibers arranged to extend in a single direction with a thermosetting resin. In this case, the fiber-reinforced fabric includes at least one of a plain weave fabric, a triaxial woven fabric and a tetra-axial woven fabric. In addition, it is possible for the UD prepreg includes a pair of oblique UD prepregs whose fiber directions are symmetrical with respect to the longitudinal direction of the shaft.
The golf club shaft according to the present invention can further include a compressive rigidity holding layer which is configured from a UD prepreg whose fiber direction is orthogonal to the longitudinal direction of the shaft, and(or) can further include a bending rigidity holding layer which is configured from a UD prepreg whose fiber direction is parallel to the longitudinal direction of the shaft.
The golf club shaft according to the present invention further includes a decorative layer which is included in an outermost layer of the shaft and configured from a UD prepreg whose fiber direction is parallel to the longitudinal direction of the shaft.
A golf club according to the present invention includes a club head and a grip that are fixed to the golf club shaft having the above-described configuration.
According to the present invention, a golf club shaft and a golf club using such a golf club shaft can be achieved, in which the isotropy of the prepregs configuring a torsion rigidity holding layer is high and in which sufficient torsional rigidity can be secured with less number of plies of less number of prepregs.
Each embodiment of a golf club shaft according to the present invention will be hereinafter discussed with reference to the accompanying drawings. In this specification, the term “isotropy” means torsional strength without regard to the orientation of the golf club shaft.
Similar to the conventional product shown in
The torsional rigidity holding layer 20 is configured from a multilayer set prepreg 30 which is continuously wound by two turns, and the multilayer set prepreg 30 is made of a triaxial woven fabric prepreg 31 and a UD prepreg 32 which are layered on each other. Namely, the triaxial woven fabric prepreg 31 and the UD prepreg 32 are previously layered to be formed into the multilayer set prepreg 30, which in turn is wound on the compressive rigidity holding layer 11 that is wound on a conical mandrel. The bending rigidity holding layer 12 is wound onto the multilayer set prepreg 30 and thermally cured according to an ordinary method to form the golf club shaft 10. As known in the art, the prepreg of the compressive rigidity holding layer 11, the prepreg of the bending rigidity holding layer 12, the triaxial woven fabric prepreg 31 and the UD prepreg 32 are each usually formed into a flat trapezoidal shape so that the ply number is an integer across the entire length when wound on a mandrel.
As shown in
If only the triaxial woven fabric prepreg 31 is wound a plurality of turns, layers of the triaxial woven fabric prepreg 31 come in contact each other; however, gaps easily occur between the layers because the triaxial woven fabric prepreg is made by weaving yarns extending in three different directions, and therefore has bumps and dips. In contrast, bumps and dips which are created between layers are reduced if the triaxial woven fabric prepreg 31 and the UD prepreg 32 are layered to be formed into the multilayer set prepreg 30 as described in the present embodiment, which makes it possible to make displacements between layers of the triaxial woven fabric prepreg 31 and the UD prepreg 32 (displacements between fibers) extremely difficult to occur when the thermosetting resin of the prepregs is thermally cured. In addition, the triaxial woven fabric prepreg 31 and the UD prepreg 32 can be prevented from being mutually torsionally deformed because reinforced fibers extending in mutually different directions are included in the triaxial woven fabric prepreg 31 and the UD prepreg 32.
Additionally, since the triaxial woven fabric prepreg 31 and the UD prepreg 32 (32a and 32b) that are mutually different in fiber direction are wound as a set of layers, not as separate layers, the multilayer set prepreg 30 can be regarded as a single layer; consequently, the isotropy of the golf club shaft 10 can be increased. In other words, if the triaxial woven fabric prepreg 31 and the UD prepreg 32 (32a and 32b) are wound as separate layers, the isotropy of the golf club shaft 10 will be the mere sum of the isotropy of the triaxial woven fabric prepreg 31 and the isotropy of the UD prepreg 32. However, if the triaxial woven fabric prepreg 31 and the UD prepreg 32 (32a and 32b) are continuously wound while being layered onto each other, a high isotropy which dramatically exceeds the mere sum of the isotropy of the triaxial woven fabric prepreg 31 and the isotropy of the UD prepreg 32 is shown, even though the prepregs used are exactly the same. This makes it possible to achieve the golf club shaft 10 that provides a feeling close to the feeling one gets when hitting a golf ball with a steel shaft, the isotropy of which is high.
Additionally, when the triaxial woven fabric prepreg 31 and the UD prepreg 32 (32a and 32b) of the multilayer set prepreg 30 are each regarded as an independent layer, both sides of this prepreg prepregs each have a different fiber direction lying over two turns or more; accordingly, deviations between layers of each prepreg (deviations between fibers of each prepreg after it is thermally cured) can be reduced to consequently be capable of enhancing the torsional rigidity. Namely, the triaxial woven fabric prepreg 31 and the UD prepreg 32 (32a and 32b) that are respectively positioned on the inside and outside adjacent to each other press against each other to prevent themselves from moving; consequently, deviations between layers (deviations between fibers) can be reduced to thereby make it possible to enhance the torsional rigidity.
In addition to carbon fibers, alumina fibers, aramid fibers, Tyranno fibers, amorphous fibers and glass fibers, etc., can be selectively used as reinforced fibers included in the prepregs constituting the compressive rigidity holding layer 11 and the bending rigidity holding layer 12, the triaxial woven fabric prepreg 31 and the UD prepreg 32. In other words, the type of yarn used is basically not limited.
It is desirable that the yarn size of each yarn be 3K (1K denotes 1000 filaments) or less. If the yarn size exceeds 3K, the prepreg becomes excessively thick and a sufficient fiber density (thread count) may not be secured; in addition, the workability when winding the prepreg around a mandrel may deteriorate.
It is possible to basically use any kind of resin as the resin with which such reinforced fibers are impregnated. For instance, it is possible to use epoxy resin, unsaturated polyester resin, phenolic resin, vinylester resin, PEEK resin, or the like.
It is desirable that the thickness of each prepreg, specifically each UD prepreg be in the range from 0.02 to 0.25 mm and each fabric prepreg be in the range from 0.06 to 0.30 mm. If the thickness of the UD prepreg (fabric prepreg) is smaller than 0.02 mm (0.06 mm), it is difficult to obtain a satisfactory rigidity. If the thickness of the UD prepreg (fabric prepreg) exceeds 0.25 mm (0.30 mm), there is a possibility of the rigidity dispersing in the longitudinal direction of the shaft.
It is desirable that the weight of each prepreg be 400 g/m2 or less. If the weight exceeds 400 g/m2, the prepreg may become too thick, thus becoming difficult to wind around a mandrel.
It is desirable that the resin quantity of each prepreg, specifically each UD prepreg be in the range from 20 to 50 wt % and each fabric prepreg be in the range from 30 to 60 wt %. If the resin quantity of the UD prepreg (fabric prepreg) is smaller than 20 wt % (30 wt %), the resin quantity is too small, so that a satisfactory shaft may not be produced. If the resin quantity of the UD prepreg (fabric prepreg) exceeds 50 wt % (60 wt %), a sufficient rigidity may not develop if the weight of the shaft is the same.
The number of turns of the multilayer set prepreg 30 in the above illustrated embodiment is “2” but can be more than 2 on the basis of specifications required for the shaft in consideration of the physical properties of the reinforced fibers and the thermosetting resin and others.
A tetra-axial woven fabric prepreg made by impregnating a tetra-axial woven fabric with a thermosetting resin can be used instead of the triaxial woven fabric prepreg 31 or the plain weave fabric prepreg 41 in the above described embodiments.
Although the multilayer set prepreg is configured from a combination of a triaxial woven fabric prepreg and a UD prepreg, a combination of a plain weave fabric prepreg and a UD prepreg, or a combination of a tetra-axial woven fabric prepreg and a UD prepreg in the above described embodiments, these combinations are mere examples; the present invention basically is established if only reinforced fibers extending in mutually different directions are included in a plurality of prepregs in a multilayer set prepreg. Examples of available combinations of prepregs are listed below in TABLE 1.
Even if a multilayer set prepreg is configured from any of the combinations above, a high isotropy which dramatically exceeds a mere sum of the isotropy of all the prepregs is shown compared with the case where each prepreg is wound independently of another prepreg though the prepregs used are exactly the same. In addition, as a result of prepregs, which are positioned adjacent to each other on the inside and outside thereof, pressing against each other to prevent themselves from moving, deviations between layers (deviations between fibers) can be reduced to thereby make it possible to enhance the torsional rigidity.
Additionally, it is possible to provide the torsional rigidity holding layer with rigidity against compression (crushing) and bending by making a multilayer set prepreg include a UD prepreg of a 0-degree layer whose fiber direction is parallel to the longitudinal direction of the shaft and a UD prepreg of a 90-degree layer whose fiber direction is orthogonal to the longitudinal direction of the shaft.
Although the compressive rigidity holding layer 11, the torsional rigidity holding layer(s) 20, the bending rigidity holding layer 12 and the decorative layer 13 are arranged in that order from the under (inner) layer in the above described embodiments, the upper-lower (inner-outer) positional relationship between these layers is flexible. For instance, it is possible to change the arrangement of the compressive rigidity holding layer 11 and the torsional rigidity holding layer(s) 20; namely, it is possible that the torsional rigidity holding layer(s) 20, the compressive rigidity holding layer 11, the bending rigidity holding layer 12 and the decorative layer 13 be arranged in that order from the under (inner) layer.
A golf club shaft according to the present invention and a golf club using this golf club shaft are suitably used in, e.g., playing golf.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2010-021358 | Feb 2010 | JP | national |
This application claims the priority of Japanese patent application No. 2010-021358, filed on Feb. 2, 2010 and PCT Application No. PCT/JP2010/071670, filed on Dec. 3, 2010, the disclosures of which are incorporated herein by reference in their entirety.
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/JP2010/071670 | 12/3/2010 | WO | 00 | 7/30/2012 |
