Method for manufacturing golf club shaft

Abstract

To provide a forming method that does not require disposable auxiliary materials such as a wrapping tape when forming an FRP golf club shaft.SOLUTION: There is provided a method for manufacturing a golf club shaft. The method is configured such that: a tubular-shaped base material including a thermosetting prepreg wound around a core rod is placed in a cavity of an outer mold with a thermal expansion member interposed between the tubular-shaped base material and an inner wall of the cavity; temperature inside the cavity is increased while keeping this state; and the thermosetting prepreg is cured and formed while pressing the tubular-shaped base material by using the expanded thermal expansion member.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a method for manufacturing a golf club shaft. [Background technology]

[0002] A conventional method for manufacturing a fiber-reinforced plastic (hereinafter sometimes abbreviated as FRP) golf club shaft involves wrapping a prepreg containing a thermosetting resin and reinforcing fibers around the outer surface of a roughly cylindrical core rod, wrapping a highly heat-resistant wrapping tape on top of that, heating the assembly in an oven to harden the thermosetting resin and form a tubular molded body, and then removing the tape (Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 3508429 specification Summary of the Invention [Problem to be solved by the invention]

[0004] However, since wrapping tape is disposable, there are problems with costs and environmental impact, and there is a need to reduce the use of wrapping tape. In addition, in molding methods using wrapping tape, there is a problem that winding and removing the wrapping tape is time-consuming, and there is also a need to automate the process.

[0005] An object of the present invention is to provide a molding method for molding an FRP golf club shaft that does not require disposable auxiliary materials such as wrapping tape. [Means for solving the problem]

[0006] In order to solve the above problems, the present invention has the following configuration. (1) A method for manufacturing a golf club shaft, comprising: placing a tubular base material including a thermosetting prepreg wound around a core rod within a cavity of an outer mold, with a heat-expandable member interposed between the tubular base material and the inner wall of the cavity; and raising the temperature inside the cavity in this state, thereby hardening and molding the thermosetting prepreg while compressing the tubular base material with the expanded heat-expandable member. (2) The method for manufacturing a golf club shaft according to (1), wherein the thermal expansion member is a member having a generally cylindrical shape as a whole. (3) The method for manufacturing a golf club shaft according to (2), wherein the thermal expansion member is configured to be divisible into two or more pieces, and a cross section perpendicular to the longitudinal direction thereof is generally annular as a whole. (4) The method for manufacturing a golf club shaft according to (2), wherein the thermal expansion member has a slit extending in an approximately longitudinal direction and a cross section perpendicular to the longitudinal direction is approximately annular as a whole. (5) The method for manufacturing a golf club shaft according to (4), wherein the slit is formed in only a portion of the thermal expansion member in the longitudinal direction. (6) A method for manufacturing a golf club shaft as described in (1), in which the heat-expandable member is fixed to the outer periphery of the tubular base material and then inserted into the cavity, thereby positioning the heat-expandable member between the thermosetting prepreg and the inner wall of the cavity. (7) A method for manufacturing a golf club shaft as described in (1), in which the thermal expansion member is fixed to the inner wall of the cavity, and then the tubular substrate is inserted into the cavity, thereby positioning the thermal expansion member between the tubular substrate and the inner wall of the cavity. (8) The method for manufacturing a golf club shaft according to any one of (1) to (7), further comprising lowering the temperature inside the cavity and removing the tubular base material from the mold in a state in which the compression of the tubular base material by the thermally expandable member is released. (9) The thermal expansion material has a linear expansion coefficient of 1×10 -4 / °C or higher. (10) The method for manufacturing a golf club shaft according to any one of (1) to (9), wherein the thickness of the thermally expandable member is in the range of 1 to 100 times the thickness of the tubular base material. (11) A method for manufacturing a golf club shaft according to any one of (1) to (10), wherein the pressure applied to the tubular base material when the thermosetting prepreg is compressed by the heat expanding member is 0.1 MPa or more and 10 MPa or less. (12) The method for manufacturing a golf club shaft according to any one of (1) to (11), wherein the material of the thermal expansion member is silicone rubber or fluororubber. (13) The method for manufacturing a golf club shaft according to any one of (1) to (12), wherein the thermally expandable member is repeatedly used in multiple moldings without being replaced. (14) A method for manufacturing a golf club shaft according to any one of (1) to (13), which does not use disposable auxiliary materials. (15) The method for producing a golf club shaft according to any one of (1) to (14), wherein the surface of the golf club shaft is not polished after the molding. Effect of the Invention

[0007] The method for molding a golf club shaft according to the present invention eliminates the need for disposable secondary materials in the molding process. [Brief description of the drawings]

[0008] [Figure 1] 1 is a schematic perspective view showing a method for molding a golf club shaft according to one embodiment of the present invention. [Diagram 2] In the schematic oblique views showing a heat-expandable member according to one embodiment of the present invention, (a) is a schematic oblique view showing a heat-expandable member having no divisions or slits, (b) is a schematic oblique view showing a heat-expandable member configured to be divided, (c) is a schematic oblique view showing a heat-expandable member having slits extending approximately in the longitudinal direction, and (d) is a schematic oblique view showing a heat-expandable member in which slits extending approximately in the longitudinal direction are formed in only a portion of the longitudinal direction. [Diagram 3]In the schematic oblique views showing a molding method for a golf club shaft according to one embodiment of the present invention, (a) is a schematic oblique view showing how a heat-expandable member 2 is fixed to the outer periphery of a tubular substrate 3 containing a thermosetting prepreg and then inserted into a cavity of an outer mold 1, and (b) is a schematic oblique view showing how a heat-expandable member 2 is fixed to the inner periphery of an outer mold 1 and then the tubular substrate 3 containing a thermosetting prepreg is inserted into the cavity. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0010] 1 is a schematic diagram illustrating a method for molding a golf club shaft according to the present invention. The outer mold 1 is a mold having an overall cylindrical shape and has a cavity whose cross section perpendicular to the longitudinal direction is circular, i.e., a cavity having a substantially cylindrical shape.

[0011] First, the thermosetting prepreg for finally constructing the golf club shaft is wound around a core rod 4. In this specification, the substrate including the thermosetting prepreg shaped into a tubular shape in this state is referred to as a "tubular substrate."

[0012] With the tubular base material 3 inserted into the cavity of the outer mold 1, the temperature inside the cavity is raised to harden the thermosetting prepreg and form a golf club shaft, with a thermally expandable member 2 interposed between the tubular base material 3 and the inner surface of the cavity. This thermally expandable member 2 has the property of thermally expanding as the temperature inside the cavity rises. Therefore, the thermally expandable member 2 expands due to the rise in temperature inside the cavity and presses the tubular base material 3. As a result, the tubular base material 3 is subjected to pressure from the periphery toward the center, as shown by the arrow P in Figure 1. In this state, the tubular base material 3 is pressed while the thermosetting prepreg is hardened, forming a golf club shaft.

[0013] In Figs. 1 to 3, the outer mold 1 is illustrated as having a pipe shape, but it may have any shape as long as it has a substantially cylindrical cavity corresponding to the predetermined shape of a golf club shaft.

[0014] The material of the outer mold 1 is not particularly limited, but examples thereof include metals such as stainless steel, aluminum, and Invar, and fiber-reinforced composite materials.

[0015] The thermal expansion member 2 has a linear expansion coefficient of 1×10 -4 / °C or more. Examples of materials having such a linear expansion coefficient include silicone rubber, fluororubber, nitrile rubber, ethylene propylene rubber, urethane rubber, and butyl rubber. Silicon rubber and fluororubber have good releasability, so they are particularly preferred materials for the demolding process.

[0016] The thermally expandable member 2 is preferably a member having a generally cylindrical shape as a whole. The cross-sectional shape of the thermally expandable member 2 may be a closed ring shape as shown in Fig. 2(a) or a shape that can be divided into two or more parts as shown in Fig. 2(b) and has a generally ring-shaped cross section perpendicular to the longitudinal direction.

[0017] The cross-sectional shape of the thermally expandable member 2 may be a partially missing ring (Landolt ring) as shown in Fig. 2(c) or 2(d). That is, the thermally expandable member 2 may have a slit extending in the approximately longitudinal direction, and the cross section perpendicular to the longitudinal direction may be approximately annular as a whole. In this case, the slit may be formed over the entire longitudinal length of the thermally expandable member as shown in Fig. 2(c), or may be formed only in a portion of the longitudinal direction as shown in Fig. 2(d).

[0018] In this way, it is preferable to configure the heat-expandable member 2 to be separable or to have slits in the heat-expandable member 2, since this makes it easier to remove the heat-expandable member 2 after molding. In addition, the parting lines or slits in the heat-expandable member 2 function as degassing paths during molding, which is expected to have the effect of suppressing voids in the molded body.

[0019] The shape of the parting lines or slits need only extend in the approximately longitudinal direction, and may be linear, wavy, mountain-valley, spiral, etc. A linear shape is preferable since the degassing path can be minimized, while a wavy, mountain-valley, or spiral shape is preferable since the shape retention of the thermally expandable member 2 is improved and handling together with the tubular base material 3 and the outer mold 1 is facilitated.

[0020] The thickness of the thermally expandable member 2 is not particularly limited, but if it is too thin relative to the tubular base material 3, the processability during attachment and detachment tends to deteriorate, while if it is too thick, unexpected deformation occurs during thermal expansion, making it difficult to apply uniform pressure. The preferred thickness of the thermally expandable member 2 is 1 to 100 times the thickness of the tubular base material 3.

[0021] The tubular substrate 3 is obtained by winding a thermosetting prepreg containing reinforcing fibers and a thermosetting resin around a core rod 4. The thermosetting prepreg preferably contains a unidirectional prepreg containing reinforcing fibers aligned in one direction, and may further contain a prepreg other than the unidirectional prepreg, for example, a prepreg containing a woven fabric.

[0022] The type of thermosetting resin of the thermosetting prepreg is not particularly limited, and examples thereof include epoxy resin, unsaturated polyester resin, phenol resin, vinyl ester resin, cyanate ester resin, bismaleimide resin, and polyimide resin. Among these, epoxy resin is preferable. Two or more of these resins may be mixed together.

[0023] The reinforcing fibers contained in the thermosetting prepreg are not particularly limited, and glass fibers, carbon fibers, aramid fibers, boron fibers, alumina fibers, silicon carbide fibers, etc. can be used. Two or more of these fibers may be mixed. Among them, carbon fibers are preferred from the viewpoint of obtaining a molded product that is lightweight and has high rigidity.

[0024] The pressure P applied to the thermosetting prepreg when the thermally expandable member 2 presses the tubular base material is not particularly limited as long as the golf club shaft after the tubular base material 3 is hardened is molded to the target thickness, but if the pressure is too small, it may not be possible to mold it to the target thickness or to a uniform thickness, and if the pressure is too large, it may have an unexpected effect on the golf club shaft. The preferred pressure range is 0.1 MPa or more and 10 MPa or less.

[0025] Although the cross section perpendicular to the longitudinal direction of the core rod 4 is illustrated as being circular, the cross section may be configured to change in the longitudinal direction to match the shape of the golf club shaft. The core rod 4 may also be hollow and approximately pipe-shaped, or solid and approximately cylindrical. The material of the core rod 4 is not particularly limited, but examples include metals such as stainless steel, aluminum, and invar, and fiber-reinforced composite materials.

[0026] 3(a), the thermally expandable member 2 is fixed to the outer periphery of the tubular substrate 3 in advance, and then the tubular substrate 3 is inserted into the cavity together with the core rod 4. In this case, with the annular thermally expandable member 2 interposed between the cavity and the tubular substrate 3, the thermally expandable member 2 is in contact with the tubular substrate 3, but can be disposed so as to have a gap or only a partial contact with the inner wall of the cavity of the outer mold 1.

[0027] 3(b), the thermally expandable member 2 is fixed in advance to the inner wall of the cavity of the outer mold 1, and then the tubular base material 3 is inserted further inside the cavity together with the core rod 4. In this case, with the annular thermally expandable member 2 interposed between the cavity and the tubular base material 3, the thermally expandable member 2 is in contact with the inner wall of the cavity of the outer mold 1, but can be disposed with a gap or only partially in contact with the tubular base material 3.

[0028] When removing from the mold, it is preferable to lower the temperature inside the cavity of the outer mold 1 and remove from the mold in a state where the pressure applied to the tubular base material by the thermally expandable member 2 is released.

[0029] The above-described series of molding processes eliminates the need for disposable auxiliary materials such as wrapping tape, and furthermore, by repeatedly using the thermal expansion member without replacing it, it is possible to manufacture golf club shafts at low cost. In addition, compared to the case where wrapping tape or the like is used, automation is easily possible, making it easy to accommodate mass production. Furthermore, since no traces of wrapping tape or the like remain on the surface of the molded body after hardening, there is no need to polish the surface of the golf club shaft after molding. [Explanation of symbols]

[0030] 1 Outer mold 2. Thermal expansion material 21 Dividable thermal expansion member 22 Thermally expandable member having a slit formed along the entire length in the longitudinal direction 23 Thermally expandable member having a slit formed only in a portion of the longitudinal direction 3 Tubular substrate (thermosetting prepreg) 4 core rod P Pressure

Claims

1. A method for manufacturing a golf club shaft, comprising: placing a tubular base material comprising thermosetting prepreg wound around a core rod within a cavity of an outer mold, with a heat-expandable member interposed between the tubular base material and the inner wall of the cavity; and raising the temperature inside the cavity in this state, thereby hardening and molding the thermosetting prepreg while compressing the tubular base material with the expanded heat-expandable member.

2. The method for manufacturing a golf club shaft according to claim 1 , wherein the thermal expansion member is a generally cylindrical member as a whole.

3. 3. The method of manufacturing a golf club shaft according to claim 2, wherein the thermal expansion member is configured to be divisible into two or more pieces, and a cross section perpendicular to the longitudinal direction thereof is generally annular as a whole.

4. 3. The method of manufacturing a golf club shaft according to claim 2, wherein the thermal expansion member has a slit extending in a substantially longitudinal direction, and a cross section perpendicular to the longitudinal direction is generally annular.

5. The method for manufacturing a golf club shaft according to claim 4 , wherein the slit is formed only partially in the longitudinal direction of the thermal expansion member.

6. 2. The method for manufacturing a golf club shaft as described in claim 1, wherein the thermal expansion member is fixed to the outer periphery of the tubular base material and then inserted into the cavity, thereby positioning the thermal expansion member between the thermosetting prepreg and the inner wall of the cavity.

7. 2. A method for manufacturing a golf club shaft as described in claim 1, wherein the thermal expansion member is fixed to the inner wall of the cavity, and then the tubular substrate is inserted into the cavity, thereby positioning the thermal expansion member between the tubular substrate and the inner wall of the cavity.

8. 8. The method for manufacturing a golf club shaft according to claim 1, further comprising lowering the temperature inside the cavity and removing the tubular base material from the mold in a state in which the pressure applied by the thermally expandable member to the tubular base material is released.

9. The thermal expansion coefficient of the thermal expansion member is 1×10 －４ 8. The method for manufacturing a golf club shaft according to claim 1, wherein the temperature is 0.15 to 1.5° C. or higher.

10. The method for manufacturing a golf club shaft according to any one of claims 1 to 7, wherein the thickness of the thermally expandable member is in the range of 1 to 100 times the thickness of the tubular base material.

11. 8. The method for manufacturing a golf club shaft according to claim 1, wherein the pressure applied to the tubular base material when the thermosetting prepreg is compressed by the thermally expandable member is 0.1 MPa or more and 10 MPa or less.

12. The method for manufacturing a golf club shaft according to any one of claims 1 to 7, wherein the material of the thermal expansion member is silicone rubber or fluororubber.

13. The method for manufacturing a golf club shaft according to any one of claims 1 to 7, wherein the thermal expansion member is repeatedly used in a plurality of moldings without being replaced.

14. The method for manufacturing a golf club shaft according to any one of claims 1 to 7, wherein no disposable auxiliary materials are used.

15. The method for manufacturing a golf club shaft according to any one of claims 1 to 7, wherein the surface of the golf club shaft is not polished after said molding.

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