Golf Clubs

Abstract

To provide a golf club fitted with a shaft having improved appearance without causing variations in hardness. [Solution] The golf club of the present invention has a shaft 10 made of fiber-reinforced resin, and the shaft 1 is characterized by having a main body layer 10A arranged radially inside and formed of a high-temperature curing material, and an exterior-exposed layer 10C arranged radially outside thereof and formed of a low-temperature curing material.

Description

[Technical field]

[0001] The present invention relates to a golf club, and more particularly to a golf club having a shaft with a characteristic feature. Golf Clubs Regarding. [Background technology]

[0002] Conventionally, golf club shafts made of fiber reinforced plastic (hereinafter referred to as FRP) have been known. As is well known, FRP shafts are formed by winding multiple prepreg sheets, in which reinforcing fibers are impregnated with synthetic resin, around a core metal, fixing them with fastening tape, and then thermally curing the sheet to remove the core (see, for example, Patent Document 1). The current situation is that shafts formed in this way have variations in hardness after molding due to the difficulty in precisely controlling variations in the material itself, the state in which the prepreg sheet is wound around the core, the resin flow during molding, etc. For this reason, in actual manufacturing sites, the surface of the molded shaft is polished in order to keep the variation in hardness during molding within a certain range. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2018-94085 Summary of the Invention [Problem to be solved by the invention]

[0004] However, when the surface is polished to correct the variation in the stiffness of the shaft, the reinforcing fibers are broken, which is a problem. In the case of golf club shafts, there are cases where it is desired to make the forming material itself visible as an appearance (to make the orientation state of the reinforcing fibers in the outermost layer visible; also called appearance), but if the reinforcing fibers are broken, the appearance is deteriorated, so the amount of polishing of the outermost layer is set small (fine surface polishing). Therefore, if the improvement of the appearance is prioritized (the amount of polishing of the outermost layer is set small), it is necessary to accept the variation in the stiffness of the shaft, and the shaft performance must be sacrificed.

[0005] On the other hand, by wrapping a prepreg sheet made of glass fiber as the outermost layer, it is possible to expose the underlying layer of translucent glass material. However, because glass materials have a small effect on the vibration frequency, if you try to keep the vibration frequency within a certain range, it becomes necessary to wrap a large number of prepreg sheets made of glass fiber. Because glass materials are translucent (not transparent), the visibility of the base layer (exterior material) decreases, and differences in the amount of polishing cause large variations in the appearance and weight of the exterior material.

[0006] The present invention has been made in consideration of the above-mentioned problems, and provides a shaft with improved appearance without causing variations in hardness. Golf clubs The purpose is to provide. [Means for solving the problem]

[0007] In order to achieve the above objectives, The present invention is a structure in which an appearance material is disposed on the surface of a normal steel shaft to improve the appearance. It is said.In such a configuration, it is sufficient that an appearance-exposed layer formed of a fiber-reinforced resin prepreg sheet is wound around at least a partial region of the steel shaft configured as a tubular body. In this case, it is preferable to roughen the surface of the part around which the prepreg sheet is wound so that the adhesion to the steel shaft surface is improved and peeling does not occur (the appearance does not deteriorate) when the wound prepreg sheet is thermally cured. Effect of the Invention

[0008] According to the present invention, a shaft with improved appearance is attached without causing variations in hardness. Golf Clubs is obtained. [Brief description of the drawings]

[0009] [Figure 1] FIG. 2 is a front view showing an example of a golf club. [Diagram 2] FIG. 2 is a pattern diagram showing an example of the arrangement of prepreg sheets, which are the constituent materials of the shaft shown in FIG. 1. [Diagram 3] 1A is a cross-sectional view of the shaft at a portion where an appearance-exposed layer is provided, and FIG. 1B is a longitudinal cross-sectional view along the axial direction at that position. [Figure 4] 4 is a flowchart illustrating an example of a manufacturing process for a shaft. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of a golf club according to the present invention will be described with reference to the drawings. The golf club 1 shown in FIG. 1 is an example of a wood-type golf club, in which a head 30 is attached to the tip end of a shaft 10, and a grip 40 made of rubber or the like is attached to the base end of the shaft 10.

[0011] The shaft 10 is formed by a sheet winding method, and is made of FRP by winding a prepreg sheet, in which reinforcing fibers are impregnated with synthetic resin, around a core metal, and then thermally curing and removing the core metal. The prepreg sheet wound around the core metal includes a prepreg sheet (hereinafter also referred to as a main body sheet, constituting a main body layer as a laminated structure) wound over the entire length of the shaft 10, a prepreg sheet (hereinafter also referred to as a reinforcing sheet, constituting a reinforcing layer as a laminated structure) wound to partially improve the strength of the head mounting area, the grip mounting area, etc., and a prepreg sheet (hereinafter also referred to as an appearance sheet, constituting an appearance exposure layer as a laminated structure) wound radially outward of the main body layer and constituted as an exterior material that exposes the exterior appearance.

[0012] The main body sheet constituting the main body layer and the reinforcing sheet constituting the reinforcing layer may be multiple sheets. The appearance sheet constituting the appearance exposure layer may be configured to be wound around the entire length of the shaft 10, may be configured to be wound around a certain length range in the axial direction, or may not be configured to be wound around the entire circumference.

[0013] In the present invention, the base material (matrix resin) of the prepreg sheet constituting the main body sheet (reinforcing sheet) and the base material of the prepreg sheet constituting the appearance sheet are different types, and the main body sheet (reinforcing sheet) is made of a type that cures at a high temperature (hereinafter also referred to as a high-temperature curing material), and the appearance sheet is made of a type that cures at a lower temperature (hereinafter also referred to as a low-temperature curing material). This is because, when making the shaft 10, after the heat treatment process for forming the main body layer that will be the inner layer, surface polishing is performed to correct the variation in hardness, and a heat treatment process for forming the appearance exposed layer that will be the outer layer is performed on the surface-polished main layer (double molding is performed). That is, in order to prevent the main body layer in a processed state from being affected by heat (for example, softening, a decrease in viscosity, and a decrease in adhesion, etc.) when the appearance exposed layer is formed, a type that cures at a lower temperature than the main body sheet is used.

[0014] Specifically, the prepreg sheet constituting the main sheet (reinforcement sheet) is made of 120 ℃ ~130 ℃ The prepreg sheet constituting the appearance sheet is a substrate that is cured at a temperature lower than the above-mentioned curing temperature, for example, 100 ℃ Below 70, preferably ℃ ~80 ℃ A thermosetting resin (e.g., epoxy resin) that hardens near the surface is used. The reinforcing fibers constituting each prepreg sheet are not particularly limited, and may be organic fibers such as para-aromatic polyamide and high-strength polyethylene, inorganic fibers such as carbon fibers, glass fibers, boron fibers, silicon carbide fibers, and alumina fibers, or metal fibers, or may be used in combination of two or more of these fibers.

[0015] The reinforcing fibers constituting the prepreg sheet may be woven or may be aligned in one direction (axial length direction, circumferential direction, inclined direction). In this case, since the appearance sheet is an external appearance material, it is preferable to use a structure that improves the appearance, such as a plain weave, a woven fabric, or a structure with metal wires interposed therein. The resin impregnation (RC) of each prepreg sheet is not particularly limited, but it is preferable that the resin impregnation of the appearance sheet is somewhat higher than that of the main body sheet so that the adhesive strength between the appearance sheet and the main body layer molded by the main body sheet is ensured. However, if the resin impregnation is too high, it becomes sticky and difficult to work with (45% resulted in difficult work), so it is preferable to use a resin impregnation of about 30 to 40%. For example, it is possible to use a resin impregnation of about 15 to 35% for the main body sheet and a resin impregnation of about 20 to 45% for the appearance sheet.

[0016] Hereinafter, with reference to FIG. 2, a configuration example of a shaft having the above-mentioned characteristics (configuration and arrangement example of the main body sheet, reinforcing sheet, and appearance sheet wound around the core 50) will be described.

[0017] 2, the main body sheet constituting the main body layer 10A is wound around the entire length L of the shaft, and includes, from the inner layer side, a main body sheet 11 having reinforcing fibers aligned in the circumferential direction, a main body sheet 12 in which a first oblique sheet having reinforcing fibers aligned in the +45° direction with respect to the axial direction and a second oblique sheet having reinforcing fibers aligned in the -45° direction with respect to the axial direction are overlapped, and main body sheets 13, 14, and 15 having reinforcing fibers aligned in the axial direction. In this case, the number of windings of each main body sheet is not limited, and the arrangement order, pattern shape, and direction of the reinforcing fibers are also not limited. In the figure, the area indicated by L1 is the portion where the head is inserted, and the area indicated by L2 is the portion where the grip is attached.

[0018] A reinforcing sheet 17 is wound around the tip end side of the main body sheet constituting the main body layer 10A where the head is attached, forming the reinforcing layer 10B. The reinforcing sheet 17 is formed by aligning reinforcing fibers in the axial direction, but the direction of the reinforcing fibers is not limited. If necessary, a reinforcing sheet may also be wound around the base end side where the grip is attached.

[0019] The appearance sheet constituting the appearance exposed layer 10C is wound after the main body sheet and the reinforcing sheet are heated and the surface of the main body layer 10A is polished to form a tubular body. That is, in order to keep the variation in hardness within a certain range when the main body layer 10A is molded from the main body sheets 11-15, the surface of the main body layer is polished before winding (wound around the surface of the polished part). In Fig. 2, four appearance sheets 21, 22, 23, and 24 are illustrated to make the configuration of the appearance sheet easier to understand, but it is not necessary for all of these to be wound, and it is sufficient that any one of the appearance sheets is wound (any combination is also possible).

[0020] There are no particular limitations on the winding position, number of winds, arrangement of the reinforcing fibers, etc. of the appearance sheet to be wound, but appearance sheet 21 is wound around the entire length L of the shaft with the reinforcing fibers aligned in the axial direction, appearance sheet 22 is wound around the tip side of the shaft with the reinforcing fibers aligned in the axial direction, appearance sheet 23 is wound around the middle region of the shaft with the reinforcing fibers aligned in the axial direction, and appearance sheet 24 is wound around the rear end side of the shaft so as to be exposed from the grip with the reinforcing fibers aligned in the axial direction.

[0021] As described above, the appearance sheet is wound for the purpose of appearance, so it may be wound around the part where the appearance is to be improved. Also, since the main purpose is appearance, it is preferable that the thickness is as thin as possible so as not to affect the basic performance of the shaft. For this reason, as shown in Fig. 3(a)(b), it is preferable to wind the thickness T of the appearance exposure layer 10C so that it is thinner than the thickness T1 of the main body layer 10A. For example, when winding plain weave or woven fabric for the purpose of appearance, it is preferable to wind with a small number of plies, such as about one ply, but when there is a purpose such as improving rigidity, it may be wound with multiple plies.

[0022] Next, a shaft manufacturing process for molding a shaft in the arrangement pattern of prepreg sheets as shown in FIG. 2 will be described with reference to FIG. First, the first molding step is performed. In this first molding step, a release agent is applied to the core metal 50, and then the prepreg sheets (main body sheets 11-15) and the reinforcing sheet 17 made of a high-temperature curing material are wound around it by hand or mechanically using a sheet rolling machine, and a fastening tape (wrapping tape; not shown) is wound around the surface. The fastening tape is wound mainly to ensure the shape retention of the main body layer and to suppress the occurrence of voids, and is wound at a constant pressure using a tape wrapping machine while the core metal 50 around which the prepreg sheets are wound is chucked.

[0023] Next, the core bar wound with the above-mentioned main body sheet, reinforcing sheet and fastening tape is transported to a heating furnace and subjected to a heat treatment, and the matrix resin is hardened at the above-mentioned high curing temperature. Thereafter, the core is removed and the fastening tape is peeled off to form a tubular main body layer 10A.

[0024] Next, the surface of the tubular main body layer 10A is polished. This polishing is performed to adjust the variation in hardness, and can be performed by a wet belt sander or by hand polishing with sandpaper. Note that the surface of the part where the appearance sheet is wound may be roughened to improve adhesion with the appearance exposure layer.

[0025] Subsequently, the second molding step is performed. This second molding step is a process for forming the appearance exposed layer 10C on the main body layer with the polished surface. First, the main body layer 10A is fitted onto the same core metal 50 as in the first molding step, and a prepreg sheet (one or more of the appearance sheets 21 to 24) made of a low-temperature curing material is wound around it as in the first molding step, and a fastening tape (wrapping tape) is wound around the surface. In this case, in consideration of workability, it is preferable to fit the main body layer 10A onto the same core metal before winding the appearance sheet, but if the main body layer with the polished surface has rigidity and can withstand the pressure of the rolling operation of the appearance sheet, it may be fitted onto the core metal from the time of winding the fastening tape.

[0026] The core around which the appearance sheet and the fastening tape are wound is then hardened at the low hardening temperature described above. The heating temperature in this second molding step is just enough to harden the low-temperature hardening material of the appearance exposed layer 10C, so the high-temperature hardening material of the main layer 10A does not soften, and stable shaft performance can be achieved.

[0027] The core is then removed and the fastening tape is peeled off to form the shaft 10. After the fastening tape is peeled off, the surface is smoothed by fine grinding since there are spiral irregularities on the surface. A clear layer may be formed on the smoothed surface, and if necessary, a decorative layer such as letters or figures may be formed.

[0028] With the shaft of the above configuration, it is possible to improve the external appearance while maintaining the shaft's performance by adjusting the variation in shaft hardness beforehand and then adding the material for the external appearance. In other words, since the external appearance exposed layer 10C does not have fiber breakage or the like, it is possible to improve the external appearance of the surface.

[0029] In addition, the exterior exposed layer 10C is not polished to adjust the variation in hardness (the outermost layer, which has a high effect as a shaft, is not polished) as in the past, or is finely polished to the extent that the surface is roughened for painting. In this case, when performing fine polishing to the extent that the surface is roughened, it is possible to ensure the performance by using, for example, high-strength reinforced fibers with high strength expression (for example, T1100G and M40X made by Toray Industries, MR70 (both fiber names) made by Mitsubishi Chemical Corporation, prepregs fused with metal wires such as boron, etc.) or special prepreg sheets combining tungsten powder with a high specific gravity and low-temperature curing resin. Furthermore, with the double molding method as described above, it is possible to arrange a thin material that would normally be polished off by polishing in the outermost layer in order to improve the crushing strength.

[0030] The appearance exposure layer having the above-mentioned structure can be formed on the surface of a general steel shaft. In consideration of the adhesion to the steel shaft surface and the difficulty of peeling, the appearance exposure layer is preferably made of the above-mentioned low-temperature curing resin material (100 ℃ Below 70, preferably ℃ ~80 ℃ In this case, it is also preferable that the prepreg sheet constituting the appearance-exposed layer is roughened on its surface before being wound.

[0031] In this case, the roughened surface state of the steel shaft and the adhesion with the above-mentioned low-temperature curing resin material, which is the exterior material, were examined to see whether peeling occurred by changing the roughened surface state. Since peeling was not found when the exterior material was wound in one ply or more, the peeling state when the exterior material was partially wound on the surface of the steel shaft was examined using multiple samples with different roughened surface states, and slight peeling was found in a very small part when the surface roughness (Ra value) was 0.2398. Therefore, when partially winding (one ply or more is also acceptable), it is desirable to form the exterior exposure layer in a state where the surface of the corresponding part of the steel shaft is roughened to a Ra value of 0.25 or more. That is, with such a configuration, it is possible to form an exterior exposure layer with good adhesion without using a primer or the like.

[0032] If the main body layer was made of the above-mentioned high-temperature curing resin material, the peeling phenomenon did not occur even if the surface was not roughened.

[0033] Although the embodiment of the present invention has been described above, the present invention is not limited to the above embodiment and can be modified in various ways. The present invention is characterized by the shaft of a golf club, and can be applied to shafts of iron-type golf clubs and putters in addition to wood-type golf clubs. Furthermore, the above-described configuration can also be applied to tubular bodies such as fishing rods, rod holders, and landing nets, in addition to golf club shafts. [Explanation of symbols]

[0034] 1. Golf clubs 10 Shaft 10A Body layer 10B Reinforcement layer 10C Exposed layer 11~15 Main sheet 17 Reinforcement sheet 21~24 Exterior sheet 30 Head 40 Grip 50 Core wire

Claims

1. A golf club having a shaft with an exterior exposure layer formed of a fiber-reinforced resin prepreg sheet wound directly on at least a partial surface area of ​​a steel tubular body and using a low-temperature curing resin material that cures at 100°C or less, The golf club according to claim 1, wherein the surface of the steel tubular body around which the prepreg sheet is wound is roughened to an Ra value of 0.25 or more.

2. A golf club as described in claim 1, characterized in that the fiber-reinforced resin prepreg sheet is partially wrapped in less than one ply around the surface of a steel shaft whose surface has an Ra value of 0.25 or more.

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