Racket frame and racket

Abstract

A racket frame includes a face portion that is annular in plan view, a handle portion, and a shaft portion connecting the face portion and the handle portion. At least a portion of the face portion, the handle portion, and the shaft portion includes a first tubular member. The first tubular member has an inner tubular portion, an outer tubular portion surrounding the inner tubular portion, and a release layer sandwiched between the inner tubular portion and the outer tubular portion.

Description

Technical Field

[0001] This invention relates to a racket frame and a racket. Background Technology

[0002] Previously, racket frames made of fiber-reinforced plastic (FRP) were known (see, for example, Japanese Patent Application Publication No. 1-121074). Generally, such FRP racket frames are formed by thermosetting multiple prepregs stacked on top of each other, comprising a laminate of multiple fiber-reinforced resin layers from each prepreg. Adjacent fiber-reinforced resin layers in the lamination direction are bonded together without gaps. Summary of the Invention

[0003] The racket frame needs to withstand the strength and rigidity of impacts. The strength of the racket frame is roughly positively correlated with its rigidity. Ensuring the required strength of the racket frame guarantees the minimum required rigidity. That is, a racket frame with the required strength will have a higher rigidity than the minimum required rigidity. Therefore, if the required strength can be ensured while reducing rigidity, the rebound performance of the racket frame can be appropriately designed.

[0004] The main objective of this invention is to provide a racket frame and racket that can have sufficient strength while appropriately designing the rebound performance of the racket frame.

[0005] The racket frame of the present invention includes a ring-shaped face section, a grip section, and a shaft section connecting the face section and the grip section when viewed from above. At least a portion of the face section, the grip section, and the shaft section includes a tubular member. In a cross-section orthogonal to the extending direction of the tubular member, the tubular member has: an inner tubular portion; an outer tubular portion surrounding the inner tubular portion; and a peeling layer sandwiched between the inner and outer tubular portions.

[0006] In the racket frame described above, it is also possible that, in the direction of extension of the face, only a portion of the face includes the peeling layer.

[0007] In the racket frame described above, when the position of the first part of the face furthest from the grip when viewed from above is set as the 12 o'clock position, the first part of the face and the second part located at the 3 o'clock position include a peeling layer, while the third part of the face located at the 2 o'clock position does not include a peeling layer.

[0008] In the aforementioned racket frame, the entire extension direction of the face may include the peeling layer.

[0009] In the aforementioned racket frame, the peeling layer may also be partially disposed in the circumferential direction of the tubular member in a section orthogonal to the extension direction of the face.

[0010] In the aforementioned racket frame, a peeling layer may also be provided in a cross section orthogonal to the extension direction of the face, covering the entire circumference of the tubular member.

[0011] In the racket frame described above, the peeling layer may also exist between a first position and a second position in the thickness direction of the tubular member. The first position is located on the inner side at a distance of 20% of the thickness of the tubular member from the middle position, and the second position is located on the outer side at a distance of 20% of the thickness of the tubular member from the middle position.

[0012] Alternatively, a through hole can be formed in the peeling layer of the racket frame, penetrating the peeling layer in the thickness direction of the tubular member.

[0013] In the racket frame described above, the peeling layer may also include an inner layer and an outer layer stacked along the thickness direction of the tubular member, wherein the inner layer and the outer layer are not bonded to each other.

[0014] In the racket frame described above, the inner tubular portion and the outer tubular portion may each include a resin layer. The release layer may also face the resin layer of the inner tubular portion and the resin layer of the outer tubular portion, respectively.

[0015] In the racket frame described above, at least one of the inner tubular portion and the outer tubular portion may be a fiber-reinforced resin layer. Preferably, the fiber-reinforced resin layers included in the first, second, and third portions comprise fibers interconnected with each other.

[0016] In the racket frame described above, the melting point of the material constituting the release layer may also be higher than the molding temperature of the resin layer.

[0017] In the racket frame described above, at least one of the inner tubular portion and the outer tubular portion may include a metal layer. The release layer may also face the aforementioned metal layer.

[0018] The racket of the present invention includes the racket frame described above and a string stretched over the face.

[0019] The above and other objects, features, situations and advantages of the present invention will become clear from the following detailed description relating to the invention, which shall be understood in conjunction with the accompanying drawings. Attached Figure Description

[0020] Figure 1 This is a top view showing the racket frame of embodiment 1.

[0021] Figure 2 From Figure 1The cross-sectional view observed by arrow II-II in the figure.

[0022] Figure 3 yes Figure 2 A partially enlarged sectional view of region III in the diagram.

[0023] Figure 4 This is a cross-sectional view of the face of the racket frame in Embodiment 2.

[0024] Figure 5 yes Figure 4 A partially enlarged sectional view of region V in the diagram.

[0025] Figure 6 This is a diagram illustrating the manufacturing method of the racket frame according to Embodiment 2.

[0026] Figure 7 This is a cross-sectional view showing a modified example of the racket frame according to Embodiment 2.

[0027] Figure 8 This is a cross-sectional view of the face of the racket frame in Embodiment 3.

[0028] Figure 9 yes Figure 8 A magnified sectional view of region IX in the diagram.

[0029] Figure 10 This is a diagram illustrating the manufacturing method of the racket frame in Embodiment 3.

[0030] Figure 11 This is a cross-sectional view of the face of the racket frame according to embodiment 4.

[0031] Figure 12 This is a top view showing the racket frame of embodiment 5.

[0032] Figure 13 From Figure 12 The cross-sectional view observed by arrows XIII-XIII in the diagram.

[0033] Figure 14 This is a diagram illustrating the manufacturing method of the racket frame in Embodiment 5.

[0034] Figure 15 This is a diagram illustrating the peeling layer included in the face of the racket frame of Embodiment 6.

[0035] Figure 16 From Figure 15 The cross-sectional view observed by arrows XVI-XVI in the diagram.

[0036] Figure 17 This is a cross-sectional view of the face of the racket frame according to embodiment 7.

[0037] Figure 18 This is a cross-sectional view of the face of the racket frame according to embodiment 8.

[0038] Figure 19 This is a top view of the racket in embodiment 9.

[0039] Figure 20 This is a cross-sectional view of the shaft portion of the racket according to embodiment 9.

[0040] Figure 21 This is a diagram illustrating the method for evaluating compressive strength in Example 1.

[0041] Figure 22 This is a diagram illustrating the evaluation method for compressive stiffness in Example 1.

[0042] Figure 23 This is a diagram illustrating the evaluation method for the transverse spring constant in Example 3. Detailed Implementation

[0043] The embodiments of the present invention will now be described with reference to the accompanying drawings.

[0044] (Implementation Method 1)

[0045] The embodiments of the present invention will now be described. Furthermore, in the following drawings, the same or equivalent parts will be labeled with the same reference numerals, and their descriptions will not be repeated.

[0046] <Structure of the racket frame>

[0047] like Figure 1 As shown, the racket frame 101 of this embodiment includes a face 1, a shaft portion 2, and a grip portion 3. The face 1, shaft portion 2, and grip portion 3 are arranged along a first direction A. In this specification, the view of the racket frame 101 viewed from a second direction B, which is orthogonal to the first direction A, is described as a top view. The second direction B is the direction orthogonal to the hitting surface formed by stringing a string on the face 1 of the racket frame 101. Furthermore, in this specification, the extension direction C of each part of the face 1 (refer to...) will be... Figure 2 The direction orthogonal to the second direction B is recorded as the compressive direction of this part.

[0048] Face 1 has an elliptical ring shape when viewed from above. The length direction of face 1 when viewed from above is along the first direction A.

[0049] The face 1 has a first end portion 1a and a second end portion 1b in the first direction A. The first end portion 1a is the end portion (top) of the face 1 located on the side opposite to the grip portion 3 in the first direction A. The second end portion 1b is the end portion (grip end) located on the side of the grip portion 3 in the first direction A.

[0050] The shaft portion 2 has a first branch member 2A and a second branch member 2B. The grip portion 3 has a grip member 3A and a handle 3B. The first branch member 2A and the second branch member 2B branch off from the grip member 3A. The handle 3B is formed to cover the grip member 3A. The handle 3B is made of polyurethane, for example.

[0051] From different perspectives, the racket frame 101 includes a first tubular member 11 and a second tubular member 12. In a cross-section orthogonal to the extending direction C of the first tubular member 11, the first tubular member 11 has a tubular shape. A hollow portion 11c is formed inside the first tubular member 11 (see reference). Figure 2 The first tubular member 11 has: a tubular portion 11i facing the inner side of the hollow portion 11c; a tubular portion 11o surrounding the outer side of the inner tubular portion 11i; and a release layer 15 sandwiched between the inner tubular portion 11i and the outer tubular portion 11o. In this specification, the release layer 15 refers to a solid or hollow portion having an arbitrary volume greater than zero, wherein at least one of the release layer 15 and the outer tubular portion 11o, and the release layer 15 and the inner tubular portion 11i, has a non-adhesive surface. In this specification, a non-adhesive surface refers to the surface between two layers that are stacked but not fixed to each other. The non-adhesive surface can be easily observed through cross-sectional observation, etc.

[0052] The inner tubular portion 11i and the outer tubular portion 11o comprise, for example, multiple resin layers. Preferably, at least one of the multiple resin layers is a fiber-reinforced resin layer. More preferably, each of the multiple resin layers is a fiber-reinforced resin layer. In a cross-section orthogonal to the extending direction of the second tubular member 12, the second tubular member 12 has a tubular shape. The second tubular member 12 may also have the same structure as the first tubular member 11.

[0053] When viewed from above, with the position of the first end 1a of the face 1 furthest from the gripping part 3 relative to the center CP of the face 1 set at the 12 o'clock position P12, a portion of the face 1 located at least between the 7 o'clock position P7 and the 5 o'clock position P5, including the 12 o'clock position P12, is constituted by the first tubular member 11. The remaining portion of the face 1 is constituted by the second tubular member 12.

[0054] The first tubular member 11 has a portion forming part of the face 1, a portion forming part of the shaft 2, and a portion forming part of the gripping member 3A. When viewed from above, the first tubular member 11 has a shape symmetrical with respect to a central axis line extending through the first end 1a and along the first direction A. The second tubular member 12 is connected to the portion of the first tubular member 11 that forms part of the face 1.

[0055] The portion of the first tubular member 11 that forms part of the face 1 has an inner circumferential surface 11a and an outer circumferential surface 11b. Between the inner circumferential surface 11a and the outer circumferential surface 11b, a plurality of through holes (not shown) are arranged spaced apart from each other in the extending direction C of the first tubular member 11. These through holes are for passage of a string (not shown), or a loop (not shown) and string. Figure 2 As shown, a groove for receiving a cord loop is formed on the outer peripheral surface 11b of the first end 1a of the first tubular member 11. This groove extends along the extending direction C of the first tubular member 11. The groove can be formed partially or integrally on the outer peripheral surface 11b of the face 1. In the portion of the first tubular member 11 where the groove is formed, a plurality of through holes penetrate the first tubular member 11, opening into the inner peripheral surface 11a and the bottom surface of the groove, respectively.

[0056] like Figure 2 As shown, the outer tubular portion 11o of the first tubular member 11 is, for example, composed of a first group of fiber-reinforced resin layers 13. The inner tubular portion 11i of the first tubular member 11 is, for example, composed of a second group of fiber-reinforced resin layers 14. In this case, the first tubular member 11 includes: a first group of fiber-reinforced resin layers 13; a second group of fiber-reinforced resin layers 14; and a release layer 15 sandwiched between the first group of fiber-reinforced resin layers 13 and the second group of fiber-reinforced resin layers 14. Alternatively, at least one of the outer tubular portion 11o and the inner tubular portion 11i of the first tubular member 11 may also include a metal layer. Alternatively, the outer tubular portion 11o of the first tubular member 11 may also include a metal layer disposed in the thickness direction of the first tubular member 11 at a position further outward than the first group of fiber-reinforced resin layers 13. Alternatively, the tubular portion 11i inside the first tubular member 11 may also include a metal layer disposed in the thickness direction of the first tubular member 11 at a position further inside than the second group of fiber-reinforced resin layers 14 and facing the hollow portion 11c. These metal layers may also be bonded to either the first group of fiber-reinforced resin layers 13 or the second group of fiber-reinforced resin layers 14.

[0057] In a cross section orthogonal to the extension direction C of the first tubular member 11, the first group of fiber-reinforced resin layers 13, the second group of fiber-reinforced resin layers 14, and the release layer 15 each have an annular shape. The first group of fiber-reinforced resin layers 13, the second group of fiber-reinforced resin layers 14, and the release layer 15 are respectively closed in the circumferential direction relative to the central axis CA of the first tubular member 11.

[0058] like Figure 3As shown, the first group of fiber-reinforced resin layers 13 and the second group of fiber-reinforced resin layers 14 are each composed of multiple fiber-reinforced resin layers stacked on top of each other radially relative to the central axis CA. In each of the first group of fiber-reinforced resin layers 13 and the second group of fiber-reinforced resin layers 14, two adjacent fiber-reinforced resin layers in the stacking direction are fixed to each other. Each of the multiple fiber-reinforced resin layers constituting the first group of fiber-reinforced resin layers 13 is in contact with each other without gaps. Each of the multiple fiber-reinforced resin layers constituting the second group of fiber-reinforced resin layers 14 is in contact with each other without gaps.

[0059] The first group of fiber-reinforced resin layers 13 includes, for example, a first fiber-reinforced resin layer 13a, a second fiber-reinforced resin layer 13b, and a third fiber-reinforced resin layer 13c. The first fiber-reinforced resin layer 13a is disposed on the outermost side of the first group of fiber-reinforced resin layers 13 relative to the central axis CA. A portion of the outer peripheral surface of the first fiber-reinforced resin layer 13a forms the inner peripheral surface 11a of the first tubular member 11. The second fiber-reinforced resin layer 13b is disposed radially relative to the central axis CA at a position more inner than the first fiber-reinforced resin layer 13a and is adjacent to the first fiber-reinforced resin layer 13a. The second fiber-reinforced resin layer 13b is bonded to the first fiber-reinforced resin layer 13a without gaps. The third fiber-reinforced resin layer 13c is disposed on the innermost side of the first group of fiber-reinforced resin layers 13 relative to the central axis CA.

[0060] The second group of fiber-reinforced resin layers 14 includes, for example, a fourth fiber-reinforced resin layer 14a, a fifth fiber-reinforced resin layer 14b, and a sixth fiber-reinforced resin layer 14c. The fourth fiber-reinforced resin layer 14a is disposed innermost relative to the central axis CA in the second group of fiber-reinforced resin layers 14. The inner circumferential surface of the fourth fiber-reinforced resin layer 14a faces the hollow portion 11c. The fifth fiber-reinforced resin layer 14b is disposed radially relative to the central axis CA at a position further outward than the fourth fiber-reinforced resin layer 14a, and is adjacent to the fourth fiber-reinforced resin layer 14a. The fifth fiber-reinforced resin layer 14b is bonded to the fourth fiber-reinforced resin layer 14a without gaps. The sixth fiber-reinforced resin layer 14c is disposed outermost relative to the central axis CA in the second group of fiber-reinforced resin layers 14.

[0061] The third fiber-reinforcing resin layer 13c of the first group of fiber-reinforcing resin layers 13 and the sixth fiber-reinforcing resin layer 14c of the second group of fiber-reinforcing resin layers 14 are configured to sandwich a release layer 15 radially (in the thickness direction of the first tubular member 11) relative to the central axis CA. The release layer 15 is not bonded to each of the third fiber-reinforcing resin layers 13c and 14c. From a different viewpoint, non-adhesive surfaces are formed between the release layer 15 and the third fiber-reinforcing resin layer 13c, and between the release layer 15 and the sixth fiber-reinforcing resin layer 14c.

[0062] The first group of fiber-reinforced resin layers 13 and the second group of fiber-reinforced resin layers 14 each comprise a plurality of fibers and resin impregnated thereon. The plurality of fibers may include, for example, at least one selected from the group consisting of carbon fibers, glass fibers, aramid fibers, and vulcanized fibers. The resin may include, for example, at least one selected from the group consisting of epoxy resin, modified epoxy resin, unsaturated polyester resin, polyamide resin, and phenolic resin. The first group of fiber-reinforced resin layers 13 may have the same structure as the second group of fiber-reinforced resin layers 14, or it may have a different structure.

[0063] The angle formed by the extension direction of each of the multiple fibers relative to the extension direction C of the first tubular member 11 is, for example, 0 degrees or more and less than 90 degrees. In each of the first group of fiber-reinforced resin layers 13 and the second group of fiber-reinforced resin layers 14, the extension directions of the fibers between two adjacent fiber-reinforced resin layers in the lamination direction may also intersect each other. For example, the angle formed by the extension direction of the fibers in one fiber-reinforced resin layer between two adjacent fiber-reinforced resin layers in the lamination direction relative to the extension direction of the first tubular member 11 may be 0 degrees, and the angle formed by the extension direction of the fibers in the other fiber-reinforced resin layer relative to the extension direction of the first tubular member 11 may be 30 degrees. The angle formed by the extension direction of the fibers in the outermost fiber-reinforced resin layers (first fiber-reinforced resin layer 13a and fourth fiber-reinforced resin layer 14a) disposed in the above-mentioned lamination direction relative to the extension direction of the first tubular member 11 may also be greater than the angle formed by the extension direction of the fibers in the adjacent fiber-reinforced resin layers (second fiber-reinforced resin layer 13b and fifth fiber-reinforced resin layer 14b) relative to the extension direction of the first tubular member 11. For example, the former could have an angle of 30 degrees and the latter an angle of 0 degrees.

[0064] The melting point of the material constituting the release layer 15 is higher than the melting point of the resin material included in each of the first group of fiber-reinforced resin layers 13 and the second group of fiber-reinforced resin layers 14.

[0065] The release layer 15 is, for example, composed of at least one film. In this case, the material constituting the release layer 15 includes, for example, at least one selected from the group consisting of polypropylene (PP), polyethylene terephthalate (PET), polyvinyl chloride (PVC), polyethylene (PE), polyethylene naphthalate (PEN), polystyrene (PS), acrylic resin (AC), polycarbonate (PC), polyphenylene sulfide (PPS), polytetrafluoroethylene (PTFE), polyetheretherketone resin (PEEK), polyethersulfone (PES), aromatic polyamide, polyimide (PI), cellulose triacetate (TAC), and polyvinyl alcohol (PVA). Alternatively, the polypropylene may also be biaxially oriented polypropylene (OPP). The polystyrene may be biaxially oriented polystyrene (OPS).

[0066] Other than the aforementioned resin material, the material constituting the release layer 15 may also include a mold release agent. The mold release agent may include, for example, at least one selected from the group consisting of oil / silicone mold release agents, wax mold release agents, surfactants, and fluorinated mold release agents.

[0067] like Figure 3 As shown, the release layer 15 exists, for example, between a first position FP and a second position SP in the stacking direction of the plurality of fiber-reinforced resin layers (the thickness direction of the first tubular member 11). The first position FP is located at a distance L from the middle position MP of the plurality of fiber-reinforced resin layers, which is 20% of the thickness T of the plurality of fiber-reinforced resin layers in the stacking direction, towards the hollow portion 11c. The second position SP is located at the middle position MP, which is at a distance L from the middle position MP, towards the side opposite to the hollow portion 11c. The middle position MP of the plurality of fiber-reinforced resin layers is the middle position between the outer peripheral surface of the first fiber-reinforced resin layer 13a and the inner peripheral surface of the fourth fiber-reinforced resin layer 14a facing the hollow portion 11c. Figure 3 The peeling layer 15 shown is disposed at the intermediate position MP. Alternatively, the peeling layer 15 may be disposed radially relative to the central axis CA at a position closer to the hollow portion 11c than at the first position FP. Alternatively, the peeling layer 15 may be disposed radially relative to the central axis CA at a position further radially than at the second position SP on the side opposite to the hollow portion 11c.

[0068] The peeling layer 15 extends, for example, between one end and the other end of the first tubular member 11 in the extending direction C. In this case, the shaft portion 2 and the grip portion 3 also include the peeling layer 15. In this case, the shaft portion 2 and the grip portion 3 become easier to bend compared to the case where the shaft portion 2 and the grip portion 3 do not include the peeling layer 15.

[0069] The second tubular member 12, for example, does not include the peeling layer 15. In this case, the portion of the face 1 formed only by the first tubular member 11 includes the peeling layer 15. Alternatively, the second tubular member 12 may also include the peeling layer 15. The peeling layer 15 may also be disposed around the entire periphery of the face 1.

[0070] The first tubular member 11 can be formed, for example, by the following method. First, a laminate of multiple prepreg sheets formed as multiple fiber-reinforced resin layers and a film formed as a release layer 15 is prepared and wound around the core material. With the laminate wound around the core material, one end of the film formed as the release layer 15 in the short side direction is connected to the other end of the film formed as the release layer 15 in the short side direction.

[0071] Second, the laminate wound around the core material is heated inside the mold and then removed. The heating temperature (molding temperature) for the laminate is above the curing temperature of the resin material included in each of the first group of fiber-reinforced resin layers 13 and the second group of fiber-reinforced resin layers 14, and below the melting point of the resin material included in the release layer 15. The heating is performed, for example, while the laminate is pressurized along its lamination direction.

[0072] Thus, in each of the first group of fiber-reinforced resin layers 13 and the second group of fiber-reinforced resin layers 14, two adjacent fiber-reinforced resin layers in the lamination direction are fixed to each other. On the other hand, the release layer 15 is not fixed to each of the first group of fiber-reinforced resin layers 13 and the second group of fiber-reinforced resin layers 14.

[0073] <The effect of racket frame 101>

[0074] In the racket frame 101, the face 1 includes a release layer 15 sandwiched between a first group of fiber-reinforced resin layers 13 and a second group of fiber-reinforced resin layers 14.

[0075] In each of the first group of fiber-reinforced resin layers 13 and the second group of fiber-reinforced resin layers 14, two adjacent fiber-reinforced resin layers in the lamination direction are fixed to each other. Therefore, when the face 1 deforms upon impact, each of the first group of fiber-reinforced resin layers 13 and the second group of fiber-reinforced resin layers 14 becomes an integral unit and moves. On the other hand, the release layer 15 is not fixed to each of the first group of fiber-reinforced resin layers 13 and the second group of fiber-reinforced resin layers 14. Therefore, when the face 1 deforms upon impact, the first group of fiber-reinforced resin layers 13 and the second group of fiber-reinforced resin layers 14, which contain the release layer 15, can move independently of each other. As a result, the rigidity of the portion of the face 1 with the release layer 15 is lower than the rigidity of the portion of the face 1 without the release layer 15.

[0076] On the other hand, the total thickness of the plurality of fiber-reinforced resin layers in the portion of face 1 where the release layer 15 is disposed is greater than the total thickness of the plurality of fiber-reinforced resin layers that differ from that portion only in that they do not include the release layer 15. This is because, in a laminate of multiple fiber-reinforced resin layers, in order to reduce rigidity without the release layer 15, the total thickness needs to be reduced. As a result, the former has higher strength than the latter.

[0077] That is, in the racket frame 101, rigidity can be reduced while ensuring the required strength, so the rebound performance, spin performance, and vibration performance (feel of hitting the ball) can be appropriately designed.

[0078] In the racket frame 101, only the first tubular member 11, which constitutes the face 1, includes a release layer 15. As described above, the second tubular member 12 may also include a release layer 15, but the release layer 15 needs to be properly configured so that the rigidity of the face 1 is not excessively reduced.

[0079] In the racket frame 101, the portion of the face 1 between at least the seven o'clock position P7 and the five o'clock position P5, including the twelve o'clock position P12, is formed by a first tubular member 11 and includes a release layer 15. Therefore, in the racket frame 101, compared to a comparative example racket frame that does not include the release layer 15 but has the same strength as the racket frame 101, the compressive stiffness of the portions of the face 1 at the twelve o'clock position P12, the three o'clock position P3, and the nine o'clock position P9 is lower.

[0080] In the racket frame 101, in a section orthogonal to the extending direction C of the face 1, the face 1 has a tubular shape, and the release layer 15 is disposed around the entire circumference of the central axis CA of the tubular shape of the face 1. In this case, the first group of fiber-reinforced resin layers 13 in the circumferential direction can move independently of the second group of fiber-reinforced resin layers 14 in the circumferential direction.

[0081] (Implementation Method 2)

[0082] The racket frame 102 of Embodiment 2 has a substantially the same structure and achieves the same effect as the racket frame 101 of Embodiment 1, but as Figure 4 As shown, the peeling layer 15 differs from the racket frame 101 in that it is partially arranged in the circumferential direction relative to the central axis CA of the face 1. The following mainly describes the differences between the racket frame 102 and the racket frame 101.

[0083] like Figure 4As shown, the release layer 15 is disposed only on the inner side (inner circumferential surface 11a side) in a section orthogonal to the extending direction C of the first tubular member 11, for example. The portion of the first tubular member 11 in which the release layer 15 is disposed has Figure 3 The layered structure shown.

[0084] On the other hand, such as Figure 5 As shown, in the portion of the first tubular member 11 without the release layer 15, the first group of fiber-reinforced resin layers 13 are fixedly bonded to the second group of fiber-reinforced resin layers 14. The third fiber-reinforced resin layer 13c of the first group of fiber-reinforced resin layers 13 is bonded to the sixth fiber-reinforced resin layer 14c of the second group of fiber-reinforced resin layers 14 without gaps.

[0085] The first tubular member 11 in Embodiment 2 can be formed in substantially the same manner as the first tubular member 11 in Embodiment 1. For example... Figure 6 As shown, in Embodiment 2, a film 25 is used as the film formed as the release layer 15, whose short-side length W2 is shorter than the short-side length W1 of the multiple prepreg sheets 23, 24 formed as multiple fiber-reinforced resin layers. The short-side length W2 of the film 25 is shorter than the circumferential length of the core material 20. Furthermore, in Figure 6 For ease of explanation, the prepreg sheet is represented by a dashed line.

[0086] <Variation Example>

[0087] In the racket frame 102, the peeling layer 15 may also be disposed only on the outer peripheral surface 11b in a section orthogonal to the extension direction of the face 1.

[0088] Alternatively, the face 1 of the racket frame 102 may include a plurality of peeling layers 15 spaced apart from each other in the circumferential direction relative to the central axis CA of the face 1. For example, as Figure 7 As shown, the release layer 15 is disposed only on the inner side (inner circumferential surface 11a side) and outer side (outer circumferential surface 11b side) in a cross section orthogonal to the extension direction C of the first tubular member 11 in the compressive direction. Each of the plurality of release layers 15 exists, for example, between the first position FP and the second position SP in the aforementioned lamination direction. The positions of the plurality of release layers 15 in the lamination direction may be the same or different from each other. Each of the plurality of release layers 15 may be sandwiched between two common fiber-reinforced resin layers or between two different fiber-reinforced resin layers.

[0089] (Implementation Method 3)

[0090] Embodiment 3: The racket frame 103 includes a structure substantially the same as that of the racket frame 101 in Embodiment 1 and achieves the same effect, but as... Figure 8As shown, the peeling layer 15 differs from the racket frame 101 in that it has overlapping regions 15c that are radially spaced apart and partially overlapped with each other relative to the central axis CA of the face 1. Hereinafter, the differences between the racket frame 103 and the racket frame 101 will be mainly explained.

[0091] like Figure 8 As shown, the release layer 15 has one end 15a and another end 15b in the circumferential direction relative to the central axis CA. One end 15a and the other end 15b are not in contact. One end 15a is positioned radially outward from the other end 15b in the radial direction relative to the central axis CA. One end 15a is spaced apart from the other end 15b in the circumferential direction relative to the central axis CA. A portion of the release layer 15 connected to the other end 15b in the aforementioned circumferential direction is arranged in a manner that is spaced apart from and overlaps with a portion of the release layer 15 connected to one end 15a in the aforementioned radial direction and in the aforementioned circumferential direction. A portion of the release layer 15 connected to one end 15a (hereinafter also referred to as the first overlapping portion 15c1) and a portion of the release layer 15 connected to the other end 15b (hereinafter also referred to as the second overlapping portion 15c2) constitute an overlapping region 15c. The position of the aforementioned overlapping region 15c in the circumferential direction is, for example, positioned on the inner circumferential surface 11a side relative to the central axis CA. Alternatively, the position of the aforementioned overlapping region 15c in the circumferential direction can also be configured relative to the central axis CA on the outer peripheral surface 11b side.

[0092] like Figure 9 As shown, the first overlapping portion 15c1 is sandwiched between the first fiber-reinforced resin layer 13a and the fourth fiber-reinforced resin layer 14a, which are the outer tubular portion 11o. The second overlapping portion 15c2 is sandwiched between the second fiber-reinforced resin layer 13b and the fifth fiber-reinforced resin layer 14b, which are the inner tubular portion 11i. A third group of fiber-reinforced resin layers 16 is disposed between the first overlapping portion 15c1 and the second overlapping portion 15c2. The third group of fiber-reinforced resin layers 16 is formed by laminating and fixing the fourth fiber-reinforced resin layer 14a, which is adjacent to the first overlapping portion 15c1 in the above-mentioned lamination direction, and the second fiber-reinforced resin layer 13b, which is adjacent to the second overlapping portion 15c2 in the above-mentioned lamination direction, without gaps.

[0093] The first tubular member 11 in Embodiment 3 can be formed in substantially the same manner as the first tubular member 11 in Embodiment 1. For example... Figure 10 As shown, in Embodiment 3, a film 25 is used as the film formed as the release layer 15, whose length W2 in the short side direction is longer than the circumferential length of the core material 20.

[0094] In the racket frame 103, when the face 1 deforms upon impact, the first group of fiber-reinforced resin layers 13 and the third group of fiber-reinforced resin layers 16, which sandwich the first overlapping portion 15c1 of the release layer 15, can move independently of each other. Furthermore, the third group of fiber-reinforced resin layers 16 and the second group of fiber-reinforced resin layers 14, which sandwich the second overlapping portion 15c2 of the release layer 15, can move independently of each other. As a result, in the racket frame 103, the rigidity of the portion of the face 1 with the overlapping region 15c containing the release layer 15 is lower than the rigidity of the portion of the face 1 with the release layer 15 but without the overlapping region 15c.

[0095] <Variation Example>

[0096] The racket frame 103 may have the same structure as the racket frame 102, except that the peeling layer 15 has an overlapping region 15c. In other words, in the racket frame 103, the peeling layer 15 may also be partially disposed in the circumferential direction relative to the central axis CA of the surface 1. For example, the peeling layer 15 may be disposed only on the inner circumferential surface 11a side relative to the central axis CA, and have an overlapping region 15c on the inner circumferential surface 11a side relative to the central axis CA.

[0097] (Implementation Method 4)

[0098] The racket frame 104 of Embodiment 4 has a substantially the same structure and achieves the same effect as the racket frame 101 of Embodiment 1, but as Figure 11 As shown, the peeling layer 15 comprises a first layer 15d (outer layer) and a second layer 15e (inner layer) stacked in the thickness direction of the first tubular member 11, and differs from the racket frame 101 in that a non-adhesive surface is formed between the first layer 15d and the second layer 15e. The differences between the racket frame 104 and the racket frame 101 will be explained below.

[0099] The first layer 15d is disposed between the first group of fiber-reinforced resin layers 13 and the second layer 15e. The second layer 15e is disposed between the first layer 15d and the second group of fiber-reinforced resin layers 14. Non-adhesive surfaces are formed between the first layer 15d and the first group of fiber-reinforced resin layers 13, and between the second layer 15e and the second group of fiber-reinforced resin layers 14. A non-adhesive surface is also formed between the first layer 15d and the second layer 15e.

[0100] In other words, the first layer 15d is not bonded to the fiber-reinforced resin layer 13 of the first group and the second layer 15e. The second layer 15e is not bonded to the fiber-reinforced resin layer 14 of the second group and the first layer 15d.

[0101] The first tubular member 11 of Embodiment 4 can be formed in substantially the same manner as the first tubular member 11 of Embodiment 1.

[0102] In the racket frame 104, when the face 1 deforms upon impact, the first group of fiber-reinforced resin layers 13 can move independently relative to the first layer 15d, the second group of fiber-reinforced resin layers 14 can move independently relative to the second layer 15e, and the first layer 15d and the second layer 15e can move independently of each other.

[0103] <Variation Example>

[0104] The racket frame 104 may have the same structure as the racket frame 102 or racket frame 103, except that the peeling layer 15 has a first layer 15d and a second layer 15e. In other words, in the racket frame 104, the first layer 15d and the second layer 15e of the peeling layer 15 may also be partially arranged in the circumferential direction relative to the central axis CA of the face 1. In addition, in the racket frame 104, the peeling layer 15 may also have an overlapping region 15c.

[0105] (Implementation Method 5)

[0106] The racket frame 105 of embodiment 5 has a substantially the same structure and achieves the same effect as the racket frame 101 of embodiment 1, but as... Figure 12 As shown, the portion (third part) of the face 1 at position P2, located at two points when viewed from above, differs from the racket frame 101 in that it does not include the peeling layer 15. The following mainly describes the differences between the racket frame 105 and the racket frame 101.

[0107] like Figure 12 As shown, in the racket frame 105, the portion of the face 1 at position P12 at the 12 o'clock position (first part), the portion at position P3 at the 3 o'clock position (second part), and the portion at position P9 at the 9 o'clock position include a peeling layer 15.

[0108] The peeling layer 15, for example, has a first peeling layer 151, a second peeling layer 152, and a third peeling layer 153 arranged at intervals from each other in the extending direction of the first tubular member 11. The first peeling layer 151 passes through the 12 o'clock position P12 and is arranged between the 11 o'clock position P11 and the 1 o'clock position P1. The second peeling layer 152 passes through the 3 o'clock position P3 and is arranged between the 2 o'clock position P2 and the 4 o'clock position P4. The third peeling layer 153 passes through the 9 o'clock position P9 and is arranged between the 8 o'clock position P8 and the 10 o'clock position P10.

[0109] like Figure 12 and Figure 13As shown, the portion of face 1 located at position P2 (the third portion) at two points and the portion located at position P10 at ten points do not include the peeling layer 15. For example, the portion of face 1 located between position P1 at one point and position P2 at two points, the portion located between position P4 at four points and position P5 at five points, the portion located between position P7 at seven points and position P8 at eight points, and the portion located between position P10 at ten points and position P11 at eleven points do not include the peeling layer 15.

[0110] The cross-sectional structure orthogonal to the extension direction C of the first tubular member 11 of the racket frame 105 is identical at all locations on the face 1, except for the presence or absence of the peeling layer 15. The number of multiple fiber-reinforced resin layers stacked in the first tubular member 11 is equal at all locations on the face 1. The multiple fiber-reinforced resin layers included in the portion at the 12 o'clock position (first portion), the portion at the 3 o'clock position P3 (second portion), and the portion at the 2 o'clock position P2 (third portion) of the face 1 include fibers connected in the first, second, and third portions. Preferably, the first tubular member 11 includes fibers connected from one end to the other. Alternatively, the multiple fiber-reinforced resin layers included in the first, second, and third portions of the face 1 may further include fibers that are not connected in each portion. For example, the first tubular member 11 may also include fibers connected to the first, second, and third portions, as well as fibers disposed only in the first portion.

[0111] The first tubular member 11 in Embodiment 5 can be formed in substantially the same manner as the first tubular member 11 in Embodiment 1. For example... Figure 14 As shown, in Embodiment 5, a plurality of films 25, each shorter in one direction (e.g., the length direction) than the length of the portion of the first tubular member 11 that is formed as the release layer 15, are used as the film. The plurality of films 25 are arranged spaced apart from each other in the extension direction C of the first tubular member 11 and are wound around the core material 20 together with a plurality of prepreg sheets 23, 24.

[0112] In the racket frame 105, a portion (the third portion) of the face 1 located at the two o'clock position P2 when viewed from above does not include the peeling layer 15. From the viewpoint of improving the rebound performance of the racket frame 105, it is preferable that the portions of the face 1 located at the twelve o'clock, three o'clock, and nine o'clock positions have low stiffness in the compressive direction. This allows the racket frame 105 to easily deform elastically in the first direction A and in the direction orthogonal to both the first and second directions B (lateral), thus increasing the rebound performance upon impact. On the other hand, the stiffness in the compressive direction of the portion of the face 1 located at the two o'clock position P2 does not contribute to improving the rebound performance of the racket frame 105 as much as the stiffness in the compressive direction of the portions of the face 1 located at the twelve o'clock, three o'clock, and nine o'clock positions. Furthermore, since the portion of the face 1 located at the two o'clock position P2 in the racket frame 105 does not include the peeling layer 15, this portion has higher stiffness compared to the racket frame 101, resulting in higher strength.

[0113] That is, in the racket frame 105, it is possible to achieve the same rebound performance as the racket frame 101 while also making the strength higher than that of the racket frame 101.

[0114] Furthermore, as a method to achieve a portion with relatively high rigidity and a portion with relatively low rigidity in the extension direction C of the first tubular member 11 without excluding the peeling layer 15, it is considered to vary the laminated structure of the fiber-reinforced resin layers in each portion of the extension direction of the first tubular member, and to form a thick-walled portion with a large number of fiber-reinforced resin layers and a thin-walled portion with a small number of fiber-reinforced resin layers. However, in this method, the first tubular member does not include fibers connected in each of the first, second, and third portions (from another perspective, it does not include fibers connected from one end of the first tubular member to the other), which may result in undesirable changes in rigidity and strength. In contrast, in the racket frame 105, since the first tubular member 11 includes fibers connected in each of the first, second, and third portions, undesirable changes in rigidity and strength are less likely to occur. In the racket frame 105, if the first tubular member 11 includes fibers connected from one end to the other, undesirable changes in rigidity and strength are even less likely to occur.

[0115] <Variation Example>

[0116] Except that the part of the face 1 (third part) at the position P2 at the two points does not include the peeling layer 15, the racket frame 105 may also include the same structure as the racket frame 102, racket frame 103 or racket frame 104.

[0117] (Implementation Method 6)

[0118] The racket frame 106 of embodiment 6 has a substantially the same structure and achieves the same effect as the racket frame 101 of embodiment 1, but as Figure 15 and Figure 16 As shown, the racket frame 106 differs from the racket frame 101 in that a through hole 15f is formed in the release layer 15 along the stacking direction of the multiple fiber-reinforced resin layers. The following mainly describes the differences between the racket frame 106 and the racket frame 101.

[0119] For example, a plurality of through holes 15f are formed on the release layer 15. The plurality of through holes 15f are arranged at intervals from each other in the extending direction C of the first tubular member 11. Alternatively, it is sufficient to form at least one through hole 15f on the release layer 15. The through hole 15f is filled with resin. The third fiber-reinforced resin layer 13c is fixed to the sixth fiber-reinforced resin layer 14c inside the through hole 15f.

[0120] The first tubular member 11 in Embodiment 6 can be formed in substantially the same manner as the first tubular member 11 in Embodiment 1. In Embodiment 6, a membrane with through holes is used as the membrane formed as the release layer 15. By pressurizing and heating the laminate of the membrane and the plurality of prepreg sheets, the resin contained in the two prepreg sheets sandwiching the membrane flows into the through holes and bonds them together without gaps.

[0121] In the first tubular member 11 of the racket frame 106, the portion with through holes 15f formed in the release layer 15 has higher rigidity than the portion without through holes 15f in the release layer 15. This is because, within the through holes 15f, the third fiber-reinforced resin layer 13c and the sixth fiber-reinforced resin layer 14c are bonded together without gaps. Therefore, compared to the racket frame 101, a portion with higher rigidity can be designed in the racket frame 106.

[0122] Furthermore, compared to the portion where the third fiber-reinforced resin layer 13c and the sixth fiber-reinforced resin layer 14c are directly bonded without the release layer 15, the bonded portion of the third fiber-reinforced resin layer 13c and the sixth fiber-reinforced resin layer 14c formed within the through hole 15f is easier to peel off. For example, the bonded portion of the third fiber-reinforced resin layer 13c and the sixth fiber-reinforced resin layer 14c formed within the through hole 15f is gradually peeled off through repeated ball strikes. As a result, the rigidity of this bonded portion can be gradually reduced within the racket frame 106.

[0123] <Variation Example>

[0124] Except for the fact that the through hole 15f is formed in the peeling layer 15, the racket frame 106 may have the same structure as the racket frame 102, racket frame 103, racket frame 104 or racket frame 105.

[0125] Furthermore, in the racket frame 106, the total opening area of ​​the through holes 15f can vary depending on the position of the extension direction C of the first tubular member 11. For example, the total opening area of ​​the through holes 15f formed on the peeling layer 15 included in a portion of the face 1 at position P2 (two points) when viewed from above may be greater than the total opening area of ​​the through holes 15f formed on the peeling layer 15 included in each portion of the face 1 at positions P12 (twelfth o'clock) and P3 (three o'clock).

[0126] (Implementation Method 7)

[0127] The racket frame 107 of Embodiment 7 has a substantially the same structure and achieves the same effect as the racket frame 101 of Embodiment 1, but differs from the racket frame 101 in that one of the outer tubular portion 11o and the inner tubular portion 11i of the first tubular member 11 includes a metal layer, and the peeling layer 15 faces the metal layer. Hereinafter, the differences between the racket frame 107 and the racket frame 101 will be mainly described.

[0128] exist Figure 17 In the racket frame 107 shown, the outer tubular portion 11o of the first tubular member 11 is composed of a first metal layer 17. The first metal layer 17 is disposed further outward than the release layer 15 in the thickness direction of the first tubular member 11. Non-adhesive surfaces are formed between the release layer 15 and the first metal layer 17, and between the release layer 15 and the sixth fiber-reinforced resin layer 14c of the second group of fiber-reinforced resin layers 14.

[0129] The material constituting the first metal layer 17 can be any metallic material, including aluminum (Al).

[0130] Alternatively, in the racket frame 107, the inner tubular portion 11i of the first tubular member 11 may be composed of a metal layer. The racket frame 107 may also have the same structure as any of the racket frames 102 to 106, except that one of the outer tubular portion 11o and the inner tubular portion 11i of the first tubular member 11 includes a metal layer, and the non-adhesive surface is formed between at least one of the metal layer and the release layer, and between the resin layer and the release layer.

[0131] Alternatively, in the racket frame 107, the outer tubular portion 11o of the first tubular member 11 may also include a resin layer disposed further outward in the thickness direction of the first tubular member 11 than the first metal layer 17. Alternatively, the inner tubular portion 11i of the first tubular member 11 may also include a second metal layer disposed further inward in the thickness direction of the first tubular member 11 than the second group of fiber-reinforced resin layers 14.

[0132] (Implementation Method 8)

[0133] The racket frame 108 of Embodiment 8 has a substantially the same structure and achieves the same effect as the racket frame 101 of Embodiment 1. However, it differs from the racket frame 101 in that the outer tubular portion 11o and the inner tubular portion 11i of the first tubular member 11 each include a metal layer, and the peeling layer 15 faces the respective metal layers of the outer tubular portion 11o and the inner tubular portion 11i. Hereinafter, the differences between the racket frame 108 and the racket frame 101 will be mainly described.

[0134] exist Figure 18 In the racket frame 108 shown, the outer tubular portion 11o of the first tubular member 11 is composed of a first metal layer 17, and the inner tubular portion 11i is composed of a second metal layer 18. The first tubular member 11 includes a first metal layer 17, a second metal layer 18, and a release layer 19 sandwiched between the first metal layer 17 and the second metal layer 18. Non-adhesive surfaces are formed between the first metal layer 17 and the release layer 19, and between the second metal layer 18 and the release layer 19, respectively.

[0135] The release layer 19 is, for example, a hollow layer. In this case, the release layer 19 is composed of a gas such as air. Alternatively, a portion of the release layer 19 may be a hollow layer, and the remaining portion may be a solid layer. The release layer 19 may also be entirely a solid layer. The material constituting the release layer 19 may be the same as the material that is not bonded to each of the first metal layer 17 and the second metal layer 18, or it may be the same as the material constituting the release layer 15.

[0136] Except that the outer tubular portion 11o and the inner tubular portion 11i of the first tubular member 11 each include a metal layer, the racket frame 108 may also have the same structure as any one of the racket frames 102 to 106.

[0137] In the racket frame 108, the outer tubular portion 11o of the first tubular member 11 may also include a resin layer surrounding the first metal layer 17. Alternatively, the inner tubular portion 11i of the first tubular member 11 may also include a resin layer surrounded by the second metal layer 18 and facing the hollow portion 11c.

[0138] (Implementation Method 9)

[0139] Each racket frame 101 to 108 in embodiments 1 to 8 becomes a racket by attaching a string 4 to its respective face 1.

[0140] like Figure 19As shown, the racket 110 includes, for example, a racket frame 101 and a string 4 stretched on the face 1 of the racket frame 101. Alternatively, instead of the racket frame 101, the racket 110 may include racket frames 102, 103, 104, 105, 106, 107, or 108. Furthermore, as described above, when the racket 110 includes a racket frame 101, such as... Figure 20 As shown, the first tubular member 11 constituting the shaft portion 2 also includes a peeling layer 15.

[0141] Since racket 110 includes any one of racket frames 101 to 108, the aforementioned effects of racket frames 101 to 108 can be achieved.

[0142] (Example 1)

[0143] The inventors evaluated the relationship between compressive stiffness and compressive strength of racket frames for specimens 1 to 4 shown below.

[0144] Sample 1 is a racket frame 101. Samples 2 to 4 do not include a release layer. In order to reduce compressive rigidity, the total thickness of multiple fiber-reinforced resin layers and the orientation angle of the fibers were adjusted.

[0145] like Figure 21 As shown, with the racket frames of samples 1 to 4 configured so that the first direction is vertical, in the direction towards the face ( Figure 21 A load is applied to the grip in the direction of the arrow (as shown in the image), and the compressive strength of each specimen is evaluated based on the resulting displacement. Furthermore, for each of the outer peripheral surface OUS and inner peripheral surface INS of a portion of the face at the 12 o'clock position on the racket frame of specimens 1-4, in the direction toward the central axis of the tubular member (…),… Figure 22 A load was applied in the direction of the arrow in the figure, and the compressive stiffness of each specimen was evaluated based on the resulting displacement. The results are shown in Table 1.

[0146] Table 1

[0147]

[0148] As shown in Table 1, in specimens 2 to 4 excluding the peeling layer, a tendency was confirmed that higher strength corresponds to higher compressive stiffness. On the other hand, the compressive stiffness of specimen 1 was lower than that of specimens 2 to 4, but the strength of specimen 1 was higher than that of specimens 2 and 3. According to this embodiment, in racket frames 101 to 106, it was confirmed that high rebound performance can be achieved while ensuring strength, resulting in low compressive stiffness.

[0149] (Example 2)

[0150] The inventors used a tubular member extending in a straight line before being bent into a racket frame as a test piece to evaluate the relationship between compressive stiffness and bending failure strength. Test piece 1 was a tubular member identical to the first tubular member 11 of the racket frame of sample 1. Test piece 2 was a tubular member identical to the tubular member of the racket frame of sample 2.

[0151] Test piece 3 is set as the first tubular member 11 of the racket frame 102. Test piece 4 corresponds to a modified version of the racket frame 102, and is set as the first tubular member 11 with the peeling layer 15 disposed only on the outer peripheral surface 11b side in a section orthogonal to the extension direction C of the first tubular member 11.

[0152] Test piece 5 corresponds to a modified example of racket frame 101, wherein the peeling layer 15 is disposed radially relative to the central axis CA in a first tubular member 11 at a position closer to the hollow portion 11c (inner side) than the first position FP. Test piece 6 corresponds to a modified example of racket frame 101, wherein the peeling layer 15 is disposed radially relative to the central axis CA in a first tubular member 11 at a position closer to the side opposite to the hollow portion 11c (outer side) than the first position FP.

[0153] For each tubular member of the test pieces 1 to 6 described above, the compressive stiffness was evaluated in the same manner as in Example 1. Furthermore, a three-point bending test was performed on each tubular member of the test pieces 1 to 6. In the three-point bending test, with the outer circumferential surface OUS and the inner circumferential surface INS of each tubular member facing each other in the vertical direction, and with two points of each tubular member supported on a horizontal plane, a load was applied from top to bottom to the portion located at the center between the two points, and the three-point bending failure strength was evaluated based on the maximum load at which each tubular member reached bending failure.

[0154] The evaluation results showed that the three-point bending failure strength of test pieces 1, 3-6 was equivalent to that of test piece 2. On the other hand, the compressive stiffness of test pieces 1, 3-6 was sufficiently low compared to that of test piece 2, less than 70% of the compressive stiffness of test piece 2. Furthermore, the compressive stiffness of test piece 5 was lower than that of test piece 6. The reasons for this are speculated as follows: First, the more the release layer 15 is arranged radially inward relative to the central axis CA of the first tubular member 11, the smaller the maximum diameter of the plurality of fiber-reinforced resin layers located further inward than the release layer 15 in the aforementioned radial direction, and the softer the plurality of fiber-reinforced resin layers located further inward than the release layer 15 in the aforementioned radial direction. Thus, the more the release layer 15 is arranged radially inward relative to the central axis CA of the first tubular member 11, the easier it is for the harder portions of the plurality of fiber-reinforced resin layers to move independently relative to the other portions, resulting in lower compressive stiffness.

[0155] (Example 3)

[0156] The inventors evaluated the compressive stiffness and spring constant of the racket frames of the above-mentioned specimens 1 and 5. Specimen 5 is designated as racket frame 105.

[0157] The compressive stiffness of a portion of the facet 1 at the 12 o'clock position of the specimens 1 and 5 was evaluated using the same method as that used in Example 1. Furthermore, the compressive stiffness of each portion of the facet 1 at the two o'clock, three o'clock, and four o'clock positions of the specimens 1 and 5 was evaluated based on the displacement generated when a load was applied to each of the inner circumferential surface 11a and outer circumferential surface 11b of each portion in the direction toward the central axis CA of the first tubular member 11.

[0158] Furthermore, the longitudinal spring constants of specimens 1 and 5 were evaluated using the same method as the method for evaluating compressive strength in Example 1. Additionally, the transverse spring constants of each racket frame of specimens 1 and 5 were evaluated. Specifically, as follows... Figure 23 As shown, with the hitting surface arranged in a manner that the vertical direction is the same as the horizontal direction, for each racket frame of the above-mentioned specimens 1 and 5, a load is applied to the portion of the face 1 located at the three o'clock position in the direction toward the portion located at the nine o'clock position, and the lateral spring constant of each specimen is evaluated based on the displacement generated by each portion.

[0159] The evaluation results confirmed that the longitudinal and transverse spring constants of each of the specimens 1 and 5 were equal. However, the compressive stiffness of the portion of the face 1 in specimen 5 located at point P2 was higher than that of the portion of the face 1 in specimen 1 located at point P2. That is, it was confirmed that specimen 5 had higher strength than specimen 1.

[0160] [Appendix 1] A racket frame includes a ring-shaped face when viewed from above, a grip portion, and a shaft portion connecting the face and the grip portion. At least a portion of the face, the grip portion, and the shaft portion includes a tubular member. In a cross section orthogonal to the extending direction of the tubular member, the tubular member has: an inner tubular portion; an outer tubular portion surrounding the inner tubular portion; and a peeling layer sandwiched between the inner tubular portion and the outer tubular portion.

[0161] [Note 2] In the racket frame described in Note 1, only a portion of the face includes the peeling layer in the extending direction of the face.

[0162] [Appendix 3] In the racket frame described in Appendix 2, when the position of the first part of the face furthest from the grip portion when viewed from above is set as the 12 o'clock position, the first part of the face and the second part located at the 3 o'clock position include the peeling layer, and the third part of the face located at the 2 o'clock position does not include the peeling layer.

[0163] [Note 4] In any one of Notes 1 to 3, the entire extension direction of the aforementioned face includes the aforementioned peeling layer.

[0164] [Note 5] In any one of Notes 1 to 4, in the racket frame, the peeling layer is partially disposed in the circumferential direction of the tubular member in a cross section orthogonal to the extending direction of the face.

[0165] [Note 6] In any one of Notes 1 to 4, in the racket frame, in a cross section orthogonal to the extension direction of the aforementioned face, the aforementioned peeling layer is disposed over the entire circumference of the aforementioned tubular member.

[0166] [Appendix 7] In any one of Appendices 1 to 6, the peeling layer exists between a first position and a second position in the thickness direction of the tubular member, wherein the first position is located on the inner side at a distance of 20% of the thickness of the tubular member from the middle position of the tubular member, and the second position is located on the outer side at a distance of 20% of the thickness of the tubular member from the middle position.

[0167] [Note 8] In any one of Notes 1 to 7, the racket frame has a through hole formed in the peeling layer that penetrates the peeling layer in the thickness direction of the tubular member.

[0168] [Note 9] In any one of Notes 1 to 8, the peeling layer comprises an inner layer and an outer layer stacked along the thickness direction of the tubular member, wherein the inner layer and the outer layer are not bonded to each other.

[0169] [Note 10] In any one of Notes 1 to 9, the inner tubular portion and the outer tubular portion each include a resin layer, and the release layer faces the resin layer of the inner tubular portion and the resin layer of the outer tubular portion respectively.

[0170] [Note 11] In the racket frame described in Note 3, at least one of the inner tubular portion and the outer tubular portion is a fiber-reinforced resin layer, and the fiber-reinforced resin layers included in the first portion, the second portion and the third portion include fibers connected to each other.

[0171] [Note 12] In the racket frame described in Note 10 or 11, the melting point of the material constituting the release layer is higher than the molding temperature of the resin layer.

[0172] [Note 13] In any one of Notes 1 to 12, at least one of the inner tubular portion and the outer tubular portion includes a metal layer, and the peeling surface faces the metal layer.

[0173] [Note 14] A racket, comprising a racket frame as described in any one of Notes 1 to 13 and a string stretched on the aforementioned face.

[0174] It should be understood that although embodiments of the present invention have been described, the embodiments disclosed herein are illustrative in all respects and do not constitute a limitation. The scope of the present invention is defined by the claims and is intended to include all modifications within the meaning and scope equivalent to the claims.

Claims

1. A racket frame, The racket frame comprises: A ring-shaped face when viewed from above; a grip; and a shaft connecting the face and the grip. At least a portion of the face, the grip, and the shaft includes a tubular member. In a cross section orthogonal to the extension direction of the tubular member, the tubular member has: an inner tubular portion; an outer tubular portion surrounding the inner tubular portion; and a peeling layer sandwiched between the inner tubular portion and the outer tubular portion.

2. The racket frame as described in claim 1, characterized in that, In the direction of extension of the face, only a portion of the face includes the peeling layer.

3. The racket frame as described in claim 2, characterized in that, When the position of the first part of the face furthest from the gripping part during the top-view observation is set as the twelve o'clock position, the first part of the face and the second part located at the three o'clock position include the peeling layer, while the third part of the face located at the two o'clock position does not include the peeling layer.

4. The racket frame as described in claim 1, characterized in that, The entire extension direction of the face includes the peeling layer.

5. The racket frame as described in claim 1, characterized in that, In a cross section orthogonal to the extension direction of the face, the peeling layer is partially disposed in the circumferential direction of the tubular member.

6. The racket frame as described in claim 1, characterized in that, In a cross section orthogonal to the extension direction of the face, the peeling layer is disposed over the entire circumference of the tubular member.

7. The racket frame as described in claim 1, characterized in that, The peeling layer exists in the thickness direction of the tubular member between a first position and a second position, the first position being located inside the tubular member at a distance of 20% of the thickness of the tubular member from the middle position, and the second position being located outside the tubular member at the same distance.

8. The racket frame as described in claim 1, characterized in that, A through hole is formed in the peeling layer, penetrating the peeling layer in the thickness direction of the tubular member.

9. The racket frame as described in claim 1, characterized in that, The peeling layer comprises an inner layer and an outer layer stacked along the thickness direction of the tubular member. The inner layer and the outer layer are not bonded to each other.

10. The racket frame as described in any one of claims 1 to 9, characterized in that, The inner tubular portion and the outer tubular portion each include a resin layer. The release layer faces the resin layer of the inner tubular portion and the resin layer of the outer tubular portion, respectively.

11. The racket frame as described in claim 3, characterized in that, At least one of the inner tubular portion and the outer tubular portion is a fiber-reinforced resin layer. The fiber-reinforced resin layers included in the first part, the second part, and the third part comprise fibers that are interconnected.

12. The racket frame as described in claim 10, characterized in that, The melting point of the material constituting the release layer is higher than the molding temperature of the resin layer.

13. The racket frame as described in any one of claims 1 to 9, characterized in that, At least one of the inner tubular portion and the outer tubular portion includes a metal layer. The peeling layer faces the metal layer.

14. A racket, comprising: The racket frame according to any one of claims 1 to 9; as well as A string stretched across the face.

Images